Caring for youth with co-occurring substance use and severe psychiatric disorders: diagnostic challenges and clinical implications.

Appropriate interventions for psychiatric conditions that commonly emerge during adolescence and early adulthood play a crucial role in modifying both acute risks as well as long-term outcomes. Substance use disorder is a common comorbidity during the early stages of mood and psychotic disorders that further heightens acute risks and is considered a negative prognostic factor. New presentations of mood and psychotic symptoms with co-occurring substance use are inherently challenging to formulate due to the uncertainty surrounding the relative impact of multiple intrinsic and extrinsic factors. Given such uncertainty, it is natural for clinicians to rely on heuristics to guide assessment and management. These heuristics however may bring about premature diagnostic closure by favouring the primacy of substance use, which in turn can result in a missed window of opportunity for a timely and appropriate intervention. We caution clinicians against over-attributing early symptoms of mood and psychotic disorders to substances use alone.