  Anecdotal evidence of cannabis use by professional programmers abounds.
Recent studies have found that some professionals regularly use cannabis while
programming even for work-related tasks. However, accounts of the impacts of
cannabis on programming vary widely and are often contradictory. For example,
some programmers claim that it impairs their ability to generate correct
solutions while others claim it enhances creativity and focus. There remains a
need for an empirical understanding of the true impacts of cannabis on
programming. This paper presents the first controlled observational study of
the effects of cannabis on programming ability. Based on a within-subjects
design with over 70 participants, we find that at ecologically valid dosages,
cannabis significantly impairs programming performance. Programs implemented
while high contain more bugs and take longer to write (p < 0.05), a small to
medium effect (0.22 <= d <= 0.44). We also did not find any evidence that high
programmers generate more divergent solutions. However, programmers can
accurately assess differences in their programming performance (r = 0.59), even
when under the influence of cannabis. We hope that this research will
facilitate evidence-based policies and help developers make informed decisions
regarding cannabis use while programming.
