<p>Here are some <a href="https://www.ncbi.nlm.nih.gov/pubmed/1615114" rel="nofollow noreferrer">basics</a> on the diagnostic process:</p>

<blockquote>
  <p>There are two main sources of disagreement in
  assessing psychiatric disorder or, as Feinstein
  (1985) wrote, 'two different phases of the
  observational process'. First, in the assessment
  of psychopathology; to transform ' the observed
  phenomena into certain raw elements of descriptive
  data'. Second, disagreement arises from
  the combining of detected psychopathology to
  yield diagnoses;' In the second phase, these raw
  descriptive elements are converted into a
  category of final expression' (Feinstein, 1985).
  Efforts have been made to standardize both
  these areas. [...]</p>
</blockquote>

<p>And if this needs a quote, here's the obvious fact:</p>

<blockquote>
  <p>Lay interviewers are unable to exercise expert
  clinical judgements in making decisions about
  the presence or absence of symptoms. [...]</p>
  
  <p>There are some particular problems in attempting
  to standardize assessments of psychiatric
  disorder. Lack of insight into mental
  illness, a problem when assessing people with
  psychotic illness especially, can affect responses
  to questions. The extreme example is the deluded
  patient who will say there is nothing wrong. In
  the training of a clinical psychiatrist much stress
  is put on obtaining historical details from
  informants other than the patient because of
  clinical evidence that those with severe mental
  illness can be misleading historians. For
  example, a subject with a delusion of persecution,
  may state that neighbours are deliberately
  making loud noises, or moving furniture in
  order to annoy. Such statements would lead
  most clinicians to investigate further by means
  of informants, though others might rely purely
  on clinical impressions from an interview.
  Attempts to standardize assessments of psychosis
  are more difficult and of a different nature
  from the problems of standardizing minor
  psychiatric disorder when insight is rarely
  impaired to an extent which affects the validity
  of self-report. A similar problem arises when
  attempting to standardize assessments of conversion
  hysteria or other physical disorders with
  a presumed psychological aetiology.</p>
</blockquote>

<p>It's not a slam dunk that standazing the interviewing process will eliminate experience as a factor, for example</p>

<blockquote>
  <p>There are also concerns that lay interviewers
  are an important source of bias when using the
  PSE. Lay interviewers tend to score more highly
  than psychiatrists and so estimate a higher
  prevalence of psychiatric disorder. For example,
  Sturt et al. (1981) found that the mean PSE
  scores for lay interviewers were nearly 30%
  higher (4-12 v. 3-20) than those of the psychiatrically
  trained interviewers. Trends in a similar
  direction and of a similar magnitude have also
  been described by Rodgers &amp; Mann (1986),
  Wing et al. (1977) and Cooper et al. (1977).</p>
</blockquote>

<p>PSE is the former name of <a href="https://en.wikipedia.org/wiki/SCAN" rel="nofollow noreferrer">SCAN</a> more or less the WHO-equivalent of the more commonly used <a href="https://en.wikipedia.org/wiki/Structured_Clinical_Interview_for_DSM-IV" rel="nofollow noreferrer">SCID</a>. Both are semi-structured interviews in which open-ended questions may be asked, but the SCID allows more freedom, including skips and completely novel questions from the interviewer.</p>

<p>With this long preamble, there has been a <em>lot</em> of research on instruments that would allow a layman to diagnose mental disorders with <em>some</em> level of reliability. These include <a href="https://www.ncbi.nlm.nih.gov/pubmed/15554572/" rel="nofollow noreferrer">CIS-R, CIDI</a>, and even the older <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821376/" rel="nofollow noreferrer">GHQ</a>. These generally have a short[er] format and don't try to cover an entire diagnostic manual.</p>

<p>Trying to produce something that would beat the SCID (or even the SCAN) with lay interviewers didn't go well, insofar. Probably the most substantive effort was NIMH's <a href="https://doi.org/10.1017/S0033291700049151" rel="nofollow noreferrer">DIS</a>; the combination of its complexity (trying to assess the majority of  DSM-III diagnoses) and use of lay interviewers didn't go well. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3966528/" rel="nofollow noreferrer">E.g.</a>,</p>

<blockquote>
  <p>Eaton et al., (2000) reported on 349 subjects reinterviewed by psychiatrists using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) following a DIS interview. Results indicated that the DIS missed many cases judged to meet criteria for diagnosis using the SCAN (29% sensitivity), and agreement between the lay versus clinician administered assessments for major depressive disorder was only fair (k=0.20).</p>
</blockquote>

<p>(That's frankly understating it fair bit. A <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3900052/" rel="nofollow noreferrer">kappa</a> of 0.2 for depression is pretty abysmal.)</p>

<p><a href="https://doi.org/10.1016/B978-012343013-7/50007-0" rel="nofollow noreferrer">Besides</a></p>

<blockquote>
  <p>Due to its highly structured format, full administration of the DIS-IV typically
  requires between 90 and 150 minutes. To shorten administration time, the
  modular format makes it possible to drop evaluation of disorders that are not of
  interest in a particular study. Another option is to drop further questioning for a
  particular disorder once it is clear that the threshold number of symptoms needed
  for diagnosis will not be met. Although designed for use by nonclinician administrators,
  training for competent administration of the DIS is necessary. Trainees
  typically attend a 1-week training program at Washington University, during which they review the DIS manual, listen to didactic presentations about the
  structure and conventions of the DIS, view videotaped vignettes, complete workbook
  exercises, and conduct several practice interviews, followed by feedback
  and review. Additional supervised practice is also recommended.</p>
</blockquote>

<p>So even this layman-oriented interview is not exactly an exercise where experience and training don't matter. Basically, the obvious conclusion is that the more fine-grained your diagnostic manual is in terms of disorder classification, the more experience and training is required to use it, even with fairly standardized instruments. (Of course that doesn't even bring into discussion whether all diagnostic categories can even be reliably distinguished, even in the best of circumstances, interviewer-wise.)</p>

<p>There's not a lot of research on the use of SCID by non-professionals because its use this way is discouraged. I did find <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3449355/" rel="nofollow noreferrer">one paper</a> which did attempt this although the contrast was not with another SCID interview by a clinician, but rather with the consensus lifetime best estimate (CLBE) diagnosis (given by professionals) taken to be "gold standard". </p>

<blockquote>
  <p>The overall agreement between the SCID-derived [they mean SCID applied by a trained non-clinician] and CLBE [consensus lifetime best estimate] DSM-IV diagnoses was very low (kappa 0.18). The SCID tended to diagnose more patients with major depression and fewer with schizophrenia and schizotypal disorder. It was clear that the major source of the diagnostic differences was information variance. A brief, or sometimes monosyllabic response to a question of the structured interview was often short of crucial psychopathological information that might have been elicited in an epistemologically more adequate manner.</p>
  
  <p>Fennig et al showed a high diagnostic concordance for schizophrenia and bipolar disorder between the SCID diagnosis by non-clinician interviewers and the best consensus diagnostic estimates performed by psychiatrists. However, that particular study was limited to patients who were already diagnosed with a psychotic condition. More importantly, the SCID-elicited information also served as the main source of the best consensus estimate. This implies little information variance between psychiatrists and non-psychiatrists, i.e. clinician- and non-clinician raters made their diagnoses upon similar information. Minimizing information variance is exactly one of the cornerstones of the structured interview, but it does not guarantee the quality (validity) of the information.</p>
  
  <p>[...]</p>
  
  <p>In conclusion, this study demonstrated a poor diagnostic performance of a structured psychiatric interview conducted by a for-the-purpose trained non-clinician. Such an interview approach cannot be recommended for clinical work, due to a high proportion of misdiagnoses. The high specificity for the diagnosis of schizophrenia (100%) may suggest a limited applicability of such interviews in research with the purpose of a confirmation of an antecedent, clinician’s diagnosis.</p>
  
  <p><a href="https://i.sstatic.net/LhbQ8.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/LhbQ8.png" alt="enter image description here"></a></p>
</blockquote>

<p>What I also find interesting in this study, although not highlighted by its authors, is that the non-clinician categorized correctly all [CLBD] cases of major depression (using SCID). The [sub-]sample was rather small though (14). On other hand, he misdiagnosed a whole bunch of other [CLBD] cases (36=50-14) as being major depression. (<a href="https://en.wikipedia.org/wiki/Sensitivity_and_specificity" rel="nofollow noreferrer">High sensitivity, low specificity</a>). That's not too surprising to me because even in primary care <a href="https://www.ncbi.nlm.nih.gov/pubmed/19640579" rel="nofollow noreferrer">depression is generally overdiagnosed</a> "for every 100 unselected cases seen in primary care, there are more false positives (n=15) than either missed (n=10) or identified cases (n=10)"; physician training as well as resorting to reassessments <a href="https://doi.org/10.1016/S0140-6736(09)62051-1" rel="nofollow noreferrer">seems to lower this bias</a>.</p>

<p>And that brings me to another comparison/point I wanted to make: if it's hard for <a href="https://en.wikipedia.org/wiki/Primary_care_physician" rel="nofollow noreferrer">primary care physicians</a> to diagnose mental health problems accurately, it's not reasonable to expect laymen to do better (in similar circumstances).</p>

CC BY-SA 4.0
2019-09-17T04:56:04.523Z
Thanks for a great answer. But the surveyed mental illnesses are not psychological disorders. As it seems that [personality disorder is more about thinking and behaving patterns, and other types of mental illness are more about moods](https://psychology.stackexchange.com/q/24078/12937), would it make a difference?
Ooker
CC BY-SA 4.0
2019-04-13T12:47:07.057Z
2019-04-13T14:17:32.530Z
2019-04-13T14:17:32.530Z
got trolled too much this week
<p>It is tempting to think of medical diagnoses as a recipe. In some cases, it is a lot easier than others to see it that way. It would seem that if you have a broken leg, you have a broken leg. Unfortunately, both physical and mental health diagnoses are rarely that straightforward. </p>

<p>In mental health, when a person comes in complaining of e.g. anxiety, feeling down, prolonged grief, or having an unsatisfying love life, those things are certainly present. But in order to get to the etiology of the presenting concerns takes a good bit of work. Certain diagnoses pop up right away as likely candidates, but then you need to rule them out as there's plenty of overlap. You have to have at least 2 potential conceptualizations of what is going on, and then you rely on your experience and ability to help the patient open up more so you can observe how their mind works, how they see themselves, and how they see the world. </p>

<p>With all that in mind you can formulate what you see as the most likely diagnosis. But even then, as time goes on and you learn more about the patient, you may find yourself changing the diagnosis.</p>

<p>Taking personality disorders in particular, it is actually quite challenging  often to differentiate between borderline, dependent, narcissistic, to name a few. You really need a lot of information and a working theory of the person.</p>

CC BY-SA 4.0
2019-03-25T15:10:18.733Z
Welcome to Psychology.SE. While I generally agree with your answer, are you able to provide examples of overlap using DSM5 or ICD etc? Maybe you can provide other evidence to back your claims. We work differently to most SE sites, where we have a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified, regardless of the reader's/answerer's background. If you still have trouble with this, feel free to visit the [help] or [meta]. Unreferenced claims can lead to answers being deleted.
Chris Rogers
CC BY-SA 4.0
2019-03-25T16:07:05.107Z
A person who presents as very needy and emotional, who hasn't been able to keep a stable relationship and is sad about it could be borderline, could be histrionic, could be dependent, could simply be persistently depressed, or experiencing a double depression. Do you want me to list all the DSM-5 crtieria for each, and cross reference which ones overlap? Or perhaps I should list every behavior I think meets each criteria for each diagnosis?
Damien DuPont
CC BY-SA 4.0
2019-03-25T16:07:16.360Z
I am a licensed therapist myself and even I have to provide citations to back claims in this day and age of false information around on the internet.  This way it doesn't matter what background the reader comes from or the answerer, the information can be corroborated to be fact rather than supposition or false claims
Chris Rogers
CC BY-SA 4.0
2019-03-26T02:14:07.850Z
@ChrisRogers - Completely ignorant of this site's culture, but the answer is general, not specific, and I'm not sure references are required. Is it truly a strict policy on this site to back up general (and correct) answers with specific citations? If someone presented with chest pressure, shortness of breath, and tachycardia, it coulkd be anxiety or a cardiac etiology. Would that need references as well?
anongoodnurse
CC BY-SA 4.0
2019-03-26T05:50:41.463Z
@anongoodnurse I think the site's policy is generally the same with Medical Sciences. What is its policy about this?
Ooker
CC BY-SA 4.0
2019-03-26T05:54:25.527Z
I think what @Chris means here is that answering the question without references is like making diagnosis without a license. Regardless how correct the answer/diagnosis is, it's still lack credibility to be trusted. However, I don't discuss about the credibility either, I'm asking about building the credibility when you don't have one.
Ooker
CC BY-SA 4.0
2019-03-27T03:56:15.930Z
@Ooker - Please allow Chris Rogers to answer questions addressed to him.
anongoodnurse
CC BY-SA 4.0
2019-03-28T08:42:55.770Z
@anongoodnurse - As Ooker pointed out, the policy here is the same as MedicalSciences.SE where references are required to back all claims.  I agree that common knowledge claims don't **necessarily** need citations but where they can be challenged they need citing.  I gave an example in this answer where overlap of diagnoses can occur.  You might not be able to cite that easily, but demonstrate it using a couple of examples in the DSM or ICD etc.
Chris Rogers
CC BY-SA 4.0
2019-03-28T16:16:53.643Z
@ChrisRogers I think that's your view of the policy, not the actual policy.
Bryan Krause
CC BY-SA 4.0
2019-03-29T14:56:13.073Z
@ChrisRogers please feel free to improve upon my answer so that it meets what you feel is the proper level of exactness. After all, you appear to have in your mind an idea of what a properly cited answer to this question would look like, you are interested in this particular question, you've stated you're in basic agreement with me, you are also a licensed therapist. This would be a perfect time for you to teach a newbie how its properly done.
Damien DuPont
CC BY-SA 4.0
2019-03-29T15:03:55.850Z
I went ahead and looked over at MedicalSciences.SE. Here's what they say: 
"Answer the question Read the question carefully. What, specifically, is the question asking for? Make sure your answer provides that – or a viable alternative. The answer can be “don’t do that”, but it should also include “try this instead”. Any answer that gets the asker going in the right direction is helpful, but do try to mention any limitations, assumptions or simplifications in your answer. Brevity is acceptable, but fuller explanations are better.
Damien DuPont
CC BY-SA 4.0
2019-03-29T15:04:05.130Z
Provide context for links
Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline."   (https://medicalsciences.stackexchange.com/help/how-to-answer)
Damien DuPont
CC BY-SA 4.0
2019-04-10T13:42:20.440Z
Rather than taking this discussion to medicalsciences.stackexchange, why not rely on our own already existing discussion on this on meta? [What level of citing references or sources should be required for answers?](https://psychology.meta.stackexchange.com/questions/201/what-level-of-citing-references-or-sources-should-be-required-for-answers) and [Advice on how to write and research a good scientific answer](https://psychology.meta.stackexchange.com/q/122/21) In practice, I would add a post notice (citation needed) in case somebody highlights a specific claim that needs to be backed up.
Steven Jeuris
CC BY-SA 4.0
2019-03-25T14:58:51.010Z
2019-03-25T14:58:51.010Z
Damien DuPont
<p>As long as the criteria do match, then the diagnosis is correct. Some disorders can have overlap criteria, but a disorder should have a unique set of symptoms. If the symptoms B has match a unique set of a disorder, then we can conclude that B has it, and can conclude that the person making that conclusion correct. </p>

<hr>

<p><sub> I know this answer has no reference, but since no one explicitly confirms or disagrees with what I really ask, so I put it as an answer so everybody can vote on it. (Downvotes are welcomed.)</sub></p>

<p><sub>On the other hand, I think that this is just basic logic/epistemology, so there is no need for reference either. </sub></p>

CC BY-SA 4.0
2019-03-27T14:49:06.790Z
I think you are confusing the word "correct" in your comments and answer with the better description in your question of "legitimate". Even a clock that is stopped is correct twice a day. The reason the diagnosis would not be legitimate is that the untrained person is not trained to recognize the criteria for the diagnosis properly. It's rather moot if they sometimes get it correct, the point of a professional diagnosis is the additional training that supports it.
Bryan Krause
CC BY-SA 4.0
2019-03-28T03:02:13.973Z
I see. Do you think if the untrained one has enough experience with the person, then they can recognize the criteria properly?
Ooker
CC BY-SA 4.0
2019-03-28T04:58:35.280Z
No. That doesn't mean untrained folks can't see signs that make them concerned, but it's just simply not a diagnosis. If anything, being too close to someone/too close to a situation could make valid diagnosis impossible, even for someone trained, especially for things like personality disorders which your question references.
Bryan Krause
CC BY-SA 4.0
2019-03-28T06:07:34.917Z
hmm, that's something new to me. I have known that therapists should have a detached/professional relationship to their client to avoid transference and dual relationship, but I didn't know that it could make diagnosis impossible too. If possible, can you elaborate more, or give me the name of it? I can't google it out.
Ooker
CC BY-SA 4.0
2019-03-28T10:58:26.877Z
It's good that you try to answer your own question and thanks for your efforts on this site. However, the mod team is receiving flags and given our no self-help policy, I'm afraid answers like this promote self help both on this site and in real-life. In fact, I find it a dangerous statement you make here and I'm inclined to mod-hammer it away from this site. Having said that, and looking at the votes, I'd recommend adapting your answer accordingly.
AliceD
CC BY-SA 4.0
2019-03-28T13:31:47.787Z
@AliceD hi, thanks for your comment. Feel free to do what you find necessary. But I think having a heavily downvoted answer is better than having none? The comments from Bryan Krause are also useful. What do you mean by adapting the answer?
Ooker
CC BY-SA 4.0
2019-03-28T13:58:58.293Z
@Ooker there is an answer. Adapting = editing/changing/improving
AliceD
CC BY-SA 4.0
2019-03-28T15:53:43.067Z
@AliceD I made another answer because my concern isn't specifically addressed in Damien's. I also want to improve it, but given my current knowledge I don't know how to do that (I still have more questions until I satisfy and be readily to make a complete answer). Maybe making it a wiki post a good option?
Ooker
CC BY-SA 4.0
2019-03-27T11:01:10.730Z
2019-03-27T15:58:54.907Z
2019-03-27T15:58:54.907Z
Ooker
<p>Assuming a layman with no formal training (person A) says "person B has disorder X". A should not make such diagnosis because they don't have the training. But if A does that because it fits the definition, then wouldn't their conclusion be correct? For example, I know that for a person to have borderline personality disorder they need to have at least 5 of 9 criteria. So if B does have that, then would A be fine to conclude that B has that disorder, in spite of the fact that A isn't trained? </p>

CC BY-SA 4.0
2019-03-25T12:19:11.870Z
Whether person A is qualified or not, if diagnosis matches the necessary criteria, then the diagnosis is correct. The question then would be how valid was the criteria matching? (Do the criteria **really** match?) The thing is that for the diagnosis to have official recognition, it needs to come from a qualified diagnostician
Chris Rogers
CC BY-SA 4.0
2019-03-25T13:30:35.597Z
why wouldn't the criteria match? For example, if A sees signs that B attempt to suicide, then well, it matches one criteria? I think the criteria are just observations, so they aren't as abstract as the disorders themselves. If A make a diagnosis, then if anyone questions the diagnosis then should they ask how A comes to that conclusion?
Ooker
<clinical-psychology><training><diagnosis>
Would a diagnosis from a layman be legitimate if it follows the definition of the disorder?
Ooker
# Would a diagnosis from a layman be legitimate if it follows the definition of the disorder?

(Asked by: username_0 on 2019-03-25)

Assuming a layman with no formal training (person A) says "person B has disorder X". A should not make such diagnosis because they don't have the training. But if A does that because it fits the definition, then wouldn't their conclusion be correct? For example, I know that for a person to have borderline personality disorder they need to have at least 5 of 9 criteria. So if B does have that, then would A be fine to conclude that B has that disorder, in spite of the fact that A isn't trained?

**Tags:** clinical-psychology, training, diagnosis

> **Comments:**
> **username_1**: Whether person A is qualified or not, if diagnosis matches the necessary criteria, then the diagnosis is correct. The question then would be how valid was the criteria matching? (Do the criteria **really** match?) The thing is that for the diagnosis to have official recognition, it needs to come from a qualified diagnostician  
> **username_0**: why wouldn't the criteria match? For example, if A sees signs that B attempt to suicide, then well, it matches one criteria? I think the criteria are just observations, so they aren't as abstract as the disorders themselves. If A make a diagnosis, then if anyone questions the diagnosis then should they ask how A comes to that conclusion?  

---

## 3 answers

### Answer by username_2 on 2019-04-13. Score: 3

Here are some [basics](https://www.ncbi.nlm.nih.gov/pubmed/1615114) on the diagnostic process:

> There are two main sources of disagreement in
> assessing psychiatric disorder or, as Feinstein
> (1985) wrote, 'two different phases of the
> observational process'. First, in the assessment
> of psychopathology; to transform ' the observed
> phenomena into certain raw elements of descriptive
> data'. Second, disagreement arises from
> the combining of detected psychopathology to
> yield diagnoses;' In the second phase, these raw
> descriptive elements are converted into a
> category of final expression' (Feinstein, 1985).
> Efforts have been made to standardize both
> these areas. [...]

And if this needs a quote, here's the obvious fact:

> Lay interviewers are unable to exercise expert
> clinical judgements in making decisions about
> the presence or absence of symptoms. [...]
>
> There are some particular problems in attempting
> to standardize assessments of psychiatric
> disorder. Lack of insight into mental
> illness, a problem when assessing people with
> psychotic illness especially, can affect responses
> to questions. The extreme example is the deluded
> patient who will say there is nothing wrong. In
> the training of a clinical psychiatrist much stress
> is put on obtaining historical details from
> informants other than the patient because of
> clinical evidence that those with severe mental
> illness can be misleading historians. For
> example, a subject with a delusion of persecution,
> may state that neighbours are deliberately
> making loud noises, or moving furniture in
> order to annoy. Such statements would lead
> most clinicians to investigate further by means
> of informants, though others might rely purely
> on clinical impressions from an interview.
> Attempts to standardize assessments of psychosis
> are more difficult and of a different nature
> from the problems of standardizing minor
> psychiatric disorder when insight is rarely
> impaired to an extent which affects the validity
> of self-report. A similar problem arises when
> attempting to standardize assessments of conversion
> hysteria or other physical disorders with
> a presumed psychological aetiology.

It's not a slam dunk that standazing the interviewing process will eliminate experience as a factor, for example

> There are also concerns that lay interviewers
> are an important source of bias when using the
> PSE. Lay interviewers tend to score more highly
> than psychiatrists and so estimate a higher
> prevalence of psychiatric disorder. For example,
> Sturt et al. (1981) found that the mean PSE
> scores for lay interviewers were nearly 30%
> higher (4-12 v. 3-20) than those of the psychiatrically
> trained interviewers. Trends in a similar
> direction and of a similar magnitude have also
> been described by Rodgers & Mann (1986),
> Wing et al. (1977) and Cooper et al. (1977).

PSE is the former name of [SCAN](https://en.wikipedia.org/wiki/SCAN) more or less the WHO-equivalent of the more commonly used [SCID](https://en.wikipedia.org/wiki/Structured_Clinical_Interview_for_DSM-IV). Both are semi-structured interviews in which open-ended questions may be asked, but the SCID allows more freedom, including skips and completely novel questions from the interviewer.

With this long preamble, there has been a *lot* of research on instruments that would allow a layman to diagnose mental disorders with *some* level of reliability. These include [CIS-R, CIDI](https://www.ncbi.nlm.nih.gov/pubmed/15554572/), and even the older [GHQ](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821376/). These generally have a short[er] format and don't try to cover an entire diagnostic manual.

Trying to produce something that would beat the SCID (or even the SCAN) with lay interviewers didn't go well, insofar. Probably the most substantive effort was NIMH's [DIS](https://doi.org/10.1017/S0033291700049151); the combination of its complexity (trying to assess the majority of DSM-III diagnoses) and use of lay interviewers didn't go well. [E.g.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3966528/),

> Eaton et al., (2000) reported on 349 subjects reinterviewed by psychiatrists using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) following a DIS interview. Results indicated that the DIS missed many cases judged to meet criteria for diagnosis using the SCAN (29% sensitivity), and agreement between the lay versus clinician administered assessments for major depressive disorder was only fair (k=0.20).

(That's frankly understating it fair bit. A [kappa](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3900052/) of 0.2 for depression is pretty abysmal.)

[Besides](https://doi.org/10.1016/B978-012343013-7/50007-0)

> Due to its highly structured format, full administration of the DIS-IV typically
> requires between 90 and 150 minutes. To shorten administration time, the
> modular format makes it possible to drop evaluation of disorders that are not of
> interest in a particular study. Another option is to drop further questioning for a
> particular disorder once it is clear that the threshold number of symptoms needed
> for diagnosis will not be met. Although designed for use by nonclinician administrators,
> training for competent administration of the DIS is necessary. Trainees
> typically attend a 1-week training program at Washington University, during which they review the DIS manual, listen to didactic presentations about the
> structure and conventions of the DIS, view videotaped vignettes, complete workbook
> exercises, and conduct several practice interviews, followed by feedback
> and review. Additional supervised practice is also recommended.

So even this layman-oriented interview is not exactly an exercise where experience and training don't matter. Basically, the obvious conclusion is that the more fine-grained your diagnostic manual is in terms of disorder classification, the more experience and training is required to use it, even with fairly standardized instruments. (Of course that doesn't even bring into discussion whether all diagnostic categories can even be reliably distinguished, even in the best of circumstances, interviewer-wise.)

There's not a lot of research on the use of SCID by non-professionals because its use this way is discouraged. I did find [one paper](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3449355/) which did attempt this although the contrast was not with another SCID interview by a clinician, but rather with the consensus lifetime best estimate (CLBE) diagnosis (given by professionals) taken to be "gold standard".

> The overall agreement between the SCID-derived [they mean SCID applied by a trained non-clinician] and CLBE [consensus lifetime best estimate] DSM-IV diagnoses was very low (kappa 0.18). The SCID tended to diagnose more patients with major depression and fewer with schizophrenia and schizotypal disorder. It was clear that the major source of the diagnostic differences was information variance. A brief, or sometimes monosyllabic response to a question of the structured interview was often short of crucial psychopathological information that might have been elicited in an epistemologically more adequate manner.
>
> Fennig et al showed a high diagnostic concordance for schizophrenia and bipolar disorder between the SCID diagnosis by non-clinician interviewers and the best consensus diagnostic estimates performed by psychiatrists. However, that particular study was limited to patients who were already diagnosed with a psychotic condition. More importantly, the SCID-elicited information also served as the main source of the best consensus estimate. This implies little information variance between psychiatrists and non-psychiatrists, i.e. clinician- and non-clinician raters made their diagnoses upon similar information. Minimizing information variance is exactly one of the cornerstones of the structured interview, but it does not guarantee the quality (validity) of the information.
>
> [...]
>
> In conclusion, this study demonstrated a poor diagnostic performance of a structured psychiatric interview conducted by a for-the-purpose trained non-clinician. Such an interview approach cannot be recommended for clinical work, due to a high proportion of misdiagnoses. The high specificity for the diagnosis of schizophrenia (100%) may suggest a limited applicability of such interviews in research with the purpose of a confirmation of an antecedent, clinician’s diagnosis.
>
> [![enter image description here](https://i.sstatic.net/LhbQ8.png)](https://i.sstatic.net/LhbQ8.png)

What I also find interesting in this study, although not highlighted by its authors, is that the non-clinician categorized correctly all [CLBD] cases of major depression (using SCID). The [sub-]sample was rather small though (14). On other hand, he misdiagnosed a whole bunch of other [CLBD] cases (36=50-14) as being major depression. ([High sensitivity, low specificity](https://en.wikipedia.org/wiki/Sensitivity_and_specificity)). That's not too surprising to me because even in primary care [depression is generally overdiagnosed](https://www.ncbi.nlm.nih.gov/pubmed/19640579) "for every 100 unselected cases seen in primary care, there are more false positives (n=15) than either missed (n=10) or identified cases (n=10)"; physician training as well as resorting to reassessments [seems to lower this bias](https://doi.org/10.1016/S0140-6736(09)62051-1).

And that brings me to another comparison/point I wanted to make: if it's hard for [primary care physicians](https://en.wikipedia.org/wiki/Primary_care_physician) to diagnose mental health problems accurately, it's not reasonable to expect laymen to do better (in similar circumstances).

> **Comments:**
> **username_0**: Thanks for a great answer. But the surveyed mental illnesses are not psychological disorders. As it seems that [personality disorder is more about thinking and behaving patterns, and other types of mental illness are more about moods](https://psychology.stackexchange.com/q/24078/12937), would it make a difference?  

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### Answer by username_3 on 2019-03-25. Score: 2

It is tempting to think of medical diagnoses as a recipe. In some cases, it is a lot easier than others to see it that way. It would seem that if you have a broken leg, you have a broken leg. Unfortunately, both physical and mental health diagnoses are rarely that straightforward.

In mental health, when a person comes in complaining of e.g. anxiety, feeling down, prolonged grief, or having an unsatisfying love life, those things are certainly present. But in order to get to the etiology of the presenting concerns takes a good bit of work. Certain diagnoses pop up right away as likely candidates, but then you need to rule them out as there's plenty of overlap. You have to have at least 2 potential conceptualizations of what is going on, and then you rely on your experience and ability to help the patient open up more so you can observe how their mind works, how they see themselves, and how they see the world.

With all that in mind you can formulate what you see as the most likely diagnosis. But even then, as time goes on and you learn more about the patient, you may find yourself changing the diagnosis.

Taking personality disorders in particular, it is actually quite challenging often to differentiate between borderline, dependent, narcissistic, to name a few. You really need a lot of information and a working theory of the person.

> **Comments:**
> **username_1**: Welcome to Psychology.SE. While I generally agree with your answer, are you able to provide examples of overlap using DSM5 or ICD etc? Maybe you can provide other evidence to back your claims. We work differently to most SE sites, where we have a strict policy that all answers should be backed up with reliable references so that the answer can be independently verified, regardless of the reader's/answerer's background. If you still have trouble with this, feel free to visit the [help] or [meta]. Unreferenced claims can lead to answers being deleted.  
> **username_3**: A person who presents as very needy and emotional, who hasn't been able to keep a stable relationship and is sad about it could be borderline, could be histrionic, could be dependent, could simply be persistently depressed, or experiencing a double depression. Do you want me to list all the DSM-5 crtieria for each, and cross reference which ones overlap? Or perhaps I should list every behavior I think meets each criteria for each diagnosis?  
> **username_1**: I am a licensed therapist myself and even I have to provide citations to back claims in this day and age of false information around on the internet.  This way it doesn't matter what background the reader comes from or the answerer, the information can be corroborated to be fact rather than supposition or false claims  
> **username_4**: @ChrisRogers - Completely ignorant of this site's culture, but the answer is general, not specific, and I'm not sure references are required. Is it truly a strict policy on this site to back up general (and correct) answers with specific citations? If someone presented with chest pressure, shortness of breath, and tachycardia, it coulkd be anxiety or a cardiac etiology. Would that need references as well?  
> **username_0**: @username_4 I think the site's policy is generally the same with Medical Sciences. What is its policy about this?  
> **username_0**: I think what @Chris means here is that answering the question without references is like making diagnosis without a license. Regardless how correct the answer/diagnosis is, it's still lack credibility to be trusted. However, I don't discuss about the credibility either, I'm asking about building the credibility when you don't have one.  
> **username_4**: @username_0 - Please allow username_1 to answer questions addressed to him.  
> **username_1**: @username_4 - As username_0 pointed out, the policy here is the same as MedicalSciences.SE where references are required to back all claims.  I agree that common knowledge claims don't **necessarily** need citations but where they can be challenged they need citing.  I gave an example in this answer where overlap of diagnoses can occur.  You might not be able to cite that easily, but demonstrate it using a couple of examples in the DSM or ICD etc.  
> **username_5**: @ChrisRogers I think that's your view of the policy, not the actual policy.  
> **username_3**: @ChrisRogers please feel free to improve upon my answer so that it meets what you feel is the proper level of exactness. After all, you appear to have in your mind an idea of what a properly cited answer to this question would look like, you are interested in this particular question, you've stated you're in basic agreement with me, you are also a licensed therapist. This would be a perfect time for you to teach a newbie how its properly done.  
> **username_3**: I went ahead and looked over at MedicalSciences.SE. Here's what they say:  "Answer the question Read the question carefully. What, specifically, is the question asking for? Make sure your answer provides that – or a viable alternative. The answer can be “don’t do that”, but it should also include “try this instead”. Any answer that gets the asker going in the right direction is helpful, but do try to mention any limitations, assumptions or simplifications in your answer. Brevity is acceptable, but fuller explanations are better.  
> **username_3**: Provide context for links Links to external resources are encouraged, but please add context around the link so your fellow users will have some idea what it is and why it’s there. Always quote the most relevant part of an important link, in case the target site is unreachable or goes permanently offline."   (https://medicalsciences.stackexchange.com/help/how-to-answer)  
> **username_6**: Rather than taking this discussion to medicalsciences.stackexchange, why not rely on our own already existing discussion on this on meta? [What level of citing references or sources should be required for answers?](https://psychology.meta.stackexchange.com/questions/201/what-level-of-citing-references-or-sources-should-be-required-for-answers) and [Advice on how to write and research a good scientific answer](https://psychology.meta.stackexchange.com/q/122/21) In practice, I would add a post notice (citation needed) in case somebody highlights a specific claim that needs to be backed up.  

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### Answer by username_0 on 2019-03-27. Score: -5

As long as the criteria do match, then the diagnosis is correct. Some disorders can have overlap criteria, but a disorder should have a unique set of symptoms. If the symptoms B has match a unique set of a disorder, then we can conclude that B has it, and can conclude that the person making that conclusion correct.

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I know this answer has no reference, but since no one explicitly confirms or disagrees with what I really ask, so I put it as an answer so everybody can vote on it. (Downvotes are welcomed.)

On the other hand, I think that this is just basic logic/epistemology, so there is no need for reference either.

> **Comments:**
> **username_5**: I think you are confusing the word "correct" in your comments and answer with the better description in your question of "legitimate". Even a clock that is stopped is correct twice a day. The reason the diagnosis would not be legitimate is that the untrained person is not trained to recognize the criteria for the diagnosis properly. It's rather moot if they sometimes get it correct, the point of a professional diagnosis is the additional training that supports it.  
> **username_0**: I see. Do you think if the untrained one has enough experience with the person, then they can recognize the criteria properly?  
> **username_5**: No. That doesn't mean untrained folks can't see signs that make them concerned, but it's just simply not a diagnosis. If anything, being too close to someone/too close to a situation could make valid diagnosis impossible, even for someone trained, especially for things like personality disorders which your question references.  
> **username_0**: hmm, that's something new to me. I have known that therapists should have a detached/professional relationship to their client to avoid transference and dual relationship, but I didn't know that it could make diagnosis impossible too. If possible, can you elaborate more, or give me the name of it? I can't google it out.  
> **username_7**: It's good that you try to answer your own question and thanks for your efforts on this site. However, the mod team is receiving flags and given our no self-help policy, I'm afraid answers like this promote self help both on this site and in real-life. In fact, I find it a dangerous statement you make here and I'm inclined to mod-hammer it away from this site. Having said that, and looking at the votes, I'd recommend adapting your answer accordingly.  
> **username_0**: @username_7 hi, thanks for your comment. Feel free to do what you find necessary. But I think having a heavily downvoted answer is better than having none? The comments from username_5 are also useful. What do you mean by adapting the answer?  
> **username_7**: @username_0 there is an answer. Adapting = editing/changing/improving  
> **username_0**: @username_7 I made another answer because my concern isn't specifically addressed in Damien's. I also want to improve it, but given my current knowledge I don't know how to do that (I still have more questions until I satisfy and be readily to make a complete answer). Maybe making it a wiki post a good option?  

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