Adolescents with a history of conduct problems (CP) are at heightened risk of increased service utilization as they develop. While the mechanisms underlying this association are unclear, early CP have also been linked with peer victimization and internalizing problems. The goals of the current study were: (1) to examine peer victimization and internalizing problems as potential serial mediators explaining increased medical and psychiatric service use in adolescents with a history of childhood CP, and; (2) to explore whether the proposed mediation models vary by sex.

Participants (N = 744; 53% boys, Mage = 8.39 years) from an ongoing longitudinal study that began in 2008 in Québec, Canada were recruited and assessed for CP, service use, and other behaviours via self-, parent- and teacher-reported questionnaires. Serial mediation analyses were conducted to examine the effects of peer victimization and internalizing problems on the association between childhood CP and adolescent medical and psychiatric service use, controlling for sex and household income.

Adolescents with childhood CP reported higher medical and psychiatric service use than non-CP peers. Peer victimization and internalizing problems significantly mediated this association in both general medical and psychiatric service use models. The models did not vary by sex.

Findings support higher levels of service use in adolescents with a history of CP, mediated by peer victimization and internalizing problems. Specifically, results highlight the importance of examining peer and socioemotional factors that may explain the increased service usage observed among youth with CP, to support better health outcomes.

Evidence suggests that cannabis may be a causal factor for development of schizophrenia. We aimed to investigate whether use of antipsychotic medication, benzodiazepines, and psychiatric service use differs among patients with schizophrenia depending on whether psychosis was precipitated by a diagnosis of cannabis use disorder (CUD).

We utilized the nationwide Danish registries to identify all individuals with an incident diagnosis of schizophrenia from 1995 to 2016. We also collected information on whether first CUD diagnosis preceded schizophrenia and thus defined a group of potentially cannabis-related schizophrenia. We compared the cannabis-related schizophrenia group both with all non-cannabis-related patients with schizophrenia and with non-cannabis-related patients with schizophrenia that were propensity-score matched to cases using a range of potentially confounding variables.

We included 35 714 people with incident schizophrenia, including 4116 (11.5%) that were cannabis-related. In the unmatched-comparison analyses, there were no clear differences over time in use of antipsychotics and benzodiazepines related to whether the diagnosis of schizophrenia was cannabis-related. After propensity-score matching, use of antipsychotics and benzodiazepines was significantly lower among cannabis-related cases of schizophrenia. In the unmatched comparison, the cannabis-related group had significantly more days admitted than the non-cannabis-related group. This was markedly attenuated after propensity-score matching.

Our findings indicate the importance of considering cannabis-related cases of schizophrenia as a potentially distinct disorder in terms of prognosis. It is unclear, however, if these differences are due to different biological types of schizophrenia being compared or if they rather indicate behavioral differences such as reduced adherence and treatment-seeking.