  In this work we reanalyze the possibility of finding bound states (scalar
clouds) of a test, charged and complex-valued scalar field with mass and charge
q in the background of a Reissner-Nordstrom black hole (RNBH). In order to
determine the existence of such scalar clouds we impose suitable regularity
conditions for the scalar field at the event horizon. We find numerical
evidence for the absence of such clouds in the subextremal and extremal RNBH
when the field is massive but not self-interacting. More importantly, we put
forward a theorem that proves that such clouds cannot exist. On the other hand,
when a suitable self-interacting potential is included, the theorem no longer
applies, providing a heuristic justification behind the existence of charged
clouds (Q-clouds) that were reported recently.
