Study of illness characteristics and symptoms in a young population with psychosis can assist for understanding of their needs, and can inform service planning strategies. The aims of the current study were to describe illness characteristics and symptoms of a first episode psychosis (FEP) sample aged 25 years and under, and compare with a sample aged over 25 years.

Interviews were conducted for 437 individuals aged 16–65 years presenting with suspected psychosis between 2005 and 2012 in a defined catchment area (population of 390 000) using the Structured Clinical Interview for DSM IV to determine the presence of a psychosis diagnosis. Individuals with confirmed psychosis were assessed using standardised instruments to determine illness characteristics at first presentation.

Among the 25 years, and under FEP sample, 23.9% had their first onset of symptoms (prodromal or psychotic) before 18 years of age. After controlling for confounders, the sample aged 25 years and under had a significantly shorter log transformed duration of untreated psychosis (p=0.002), more negative symptoms (p=0.045) and greater frequency of comorbid cannabis abuse diagnosis (p=0.027).

Symptom onset in a youth FEP sample frequently occurs before age 18 years. Certain illness characteristics differed across the age categories, such as greater negative symptoms and cannabis abuse in the youth sample. Overall, the findings support the provision of adequate strategies for management of negative symptom deficits and substance abuse across all ages in FEP.

Previous studies of bipolar disorders indicate that childhood abuse and substance abuse are associated with the disorder. Whether both influence the clinical picture, or if one is mediating the association of the other, has not previously been investigated.

A total of 587 patients with bipolar disorders were recruited from Norway and France. A history of childhood abuse was obtained using the Childhood Trauma Questionnaire. Diagnosis and clinical variables, including substance abuse, were based on structured clinical interviews (Structured Clinical Interview for DSM-IV Axis I disorders or French version of the Diagnostic Interview for Genetic Studies).

Cannabis abuse was significantly associated with childhood abuse, specifically emotional and sexual abuse (χ2 = 8.63, p = 0.003 and χ2 = 7.55, p = 0.006, respectively). Cannabis abuse was significantly associated with earlier onset of the illness (z = −4.17, p < 0.001), lifetime history of at least one suicide attempt (χ2 = 11.16, p = 0.001) and a trend for rapid cycling (χ2 = 3.45, p = 0.06). Alcohol dependence was associated with suicide attempt (χ2 = 10.28, p = 0.001), but not with age at onset or rapid cycling. After correcting for possible confounders and multiple testing, a trend was observed for an interaction between cannabis abuse and childhood abuse and suicide attempt (logistic regression: r2 = 0.06, p = 0.039). Significant additive effects were also observed between cannabis abuse and childhood abuse on earlier age at onset (p < 0.001), increased rapid cycling and suicide attempt (logistic regression: r2 = 0.03–0.04, p < 0.001). No mediation effects were observed; childhood abuse and cannabis abuse were independently associated with the disorder.

Our study is the first to demonstrate significant additive effects, but no mediation effects, between childhood abuse and cannabis abuse on increased clinical expressions of bipolar disorders.