A rich body of literature dealt with somatic comorbidities of psychiatric illnesses. However, relatively few explored the association of somatic and psychiatric comorbidities with psychiatric treatment success.

Objective of this analysis was to explore chronic somatic and psychiatric comorbidities association with the average number of psychiatric re-hospitalisations annually.

This cross-sectional analysis was done on the baseline data of prospective cohort study “Somatic comorbidities in psychiatric patients” started during 2016 at Psychiatric hospital Sveti Ivan, Zagreb, Croatia. We included 798 patients. Outcome was the average number of psychiatric re-hospitalisations annually since the diagnosis. Predictors were number of chronic somatic and psychiatric comorbidities. Covariates that we controlled were sex, age, BMI, marital status, number of household members, education, work status, duration of primary psychiatric illness, CGI–severity at diagnosis, treatment with antidepressants and antipsychotics.

Interaction of somatic and psychiatric comorbidities was the strongest predictor of the average number of psychiatric re-hospitalisations annually (P < 0.001). Mean number of re-hospitalisations annually adjusted for all covariates, was increasing from 0.60 in patients with no chronic comorbidities, up to 1.10 in patients with ≥ 2 somatic and ≥ 2 psychiatric comorbidities.

Somatic and psychiatric comorbidities are independently associated with the psychiatric treatment success. Further studies should look at possible causal pathways between them, and interdisciplinary treatment of psychiatric patients is urgently needed.

The authors have not supplied their declaration of competing interest.