Association of Mediterranean diet adherence and chronotype with psychiatric symptom severity in adults treated with second-generation antipsychotics: a cross-sectional study

Lifestyle factors, including diet and circadian rhythms, are increasingly recognised as important determinants of mental health. However, the combined role of adherence to the Mediterranean diet (MD) and chronotype in relation to symptom severity in severe mental disorders remains unclear. In this multicentre cross-sectional study, 107 Italian adults (18–65 years) with schizophrenia spectrum disorders (SSD) or bipolar disorders (BD) treated with second-generation antipsychotics (SGAs) were included. MD adherence was assessed using the 14-item Prevención con Dieta Mediterránea (PREDIMED) questionnaire, chronotype with the reduced Morningness–Eveningness Questionnaire (rMEQ), and psychiatric symptoms with the Brief Psychiatric Rating Scale (BPRS). Multivariable linear regression models adjusted for age, body mass index (BMI), sex, and diagnosis were used. Participants showed moderate adherence to the MD, with similar distributions across diagnostic groups. Low consumption of fruit, fish, and nuts represented the main dietary gaps. While MD adherence showed a trend toward an inverse correlation with symptom severity in bivariant analysis, this association did not reach statistical significance in the adjusted multivariable model. In contrast, chronotype exhibited a diagnosis-specific pattern, supported by a significant interaction between diagnosis and chronotype in the multivariable model ( p = 0.016). Specifically, greater eveningness was significantly correlated with higher psychiatric symptom severity in the BD group (ρ=−0.451, p = 0.014) but not in the SSD group. Evening chronotype is associated with greater psychiatric symptom severity, especially in BD. Although MD adherence was not independently associated with symptom severity after adjusting for confounders, the identified dietary gaps highlight crucial targets for lifestyle modifications. Chronotype assessment and lifestyle recommendations may represent an important factor to consider alongside standard care in this population.