RESUMO
Suicide is a common cause of death in all phases of schizophrenia spectrum disorder, particularly in the youngest patients. Clinical measures have demonstrated limited value in suicide prediction, spurring the search for potential biomarkers. The causes of suicidal behaviour are complex, but the immune system seems to be involved as it reflects or even causes mental suffering. We aimed to identify cytokines with associations to suicidality in a sample of patients with symptoms of active psychosis. Patients with schizophrenia spectrum disorder (N = 144) participating in a semi-randomized antipsychotic drug trial (the BeSt InTro study) were assessed with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS) at eight visits across 12 months. The Clinical Global Impression for Severity of Suicidality scale (CGI-SS) was used for assessing suicidality. Serum concentrations of tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1beta, IL-2, IL-4, IL-6, and IL-10 were measured using immunoassays. A logistic regression model was used to investigate the association between cytokine levels and suicidality. To enhance clinical significance, the CGI-SS scores were dichotomized into two groups before analyses: low (=1) and high (≥2) risk for suicidality. Both uni- and multi-variate analyses revealed an inverse correlation between IL-2 and IL-10 serum levels and suicidality, where lower cytokine concentrations of IL-2 and IL-10 were associated with higher suicidality scores. The results were consistent when adjusted for depression and substance use. These results indicate that inflammatory processes are linked to the risk of suicidality in patients with schizophrenia spectrum disorders.
RESUMO
Depression occurs frequently in all phases of schizophrenia spectrum disorders. Altered activity in the immune system is seen in both depression and schizophrenia. We aimed to uncover depressive trajectories in a sample of 144 adult individuals with schizophrenia spectrum disorders followed for one year, in order to identify possible cytokine profile differences. Patients were assessed longitudinally with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS), where a score above 6 predicts depression. The serum cytokine concentrations for tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-10, IL-12p70 and IL-17A were measured using immunoassays. Latent growth curve models, multilevel models and latent class growth analysis (LCGA) were applied. The LCGA model supported three latent classes (trajectories) with differing CDSS profiles during the one-year follow-up: a high CDSS group (40.8 % of participants), a moderate CDSS group (43.9 %) and a low CDSS group (15.3 %). Five single PANSS items predicted affiliation to depressive trajectory: hallucinations, difficulty in abstract thinking, anxiety, guilt feelings and tension. In the high CDSS group, despite diminishing psychotic symptoms, depressive symptoms persisted throughout one year. The pro-inflammatory cytokines IFN-γ, IL-1ß and TNF-α were differentially distributed between the depressive trajectories, although levels remained remarkably stable throughout 12 months. Significant changes were found for the anti-inflammatory cytokine IL-10 at baseline with an accompanying difference in change over time. More research is required to optimize future treatment stratification and investigate the contribution of inflammation in depressed patients with schizophrenia spectrum disorders.