The epidemiology of the association between mental disorders and medical illnesses is the subject of many research studies, mainly due to the worse prognosis associated with this comorbidity.

To investigate the psychiatric morbidity associated with somatic diseases in liaison psychiatry outpatients and to identify factors associated with this morbidity.

A descriptive and analytical cross-sectional study was conducted. It took place at the psychiatry outpatient unit at CHU Hedi Chaker of Sfax in Tunisia. We collected 110 files of patients having a medical and/or surgical condition, addressed for the first time in 2014, as part of liaison psychiatry.

Major depressive disorder (MDD) and adjustment disorder (AD) with anxious and/or depressive mood were the most common diagnoses in liaison psychiatry (respectively 53 cases and 28 cases).

MDD has been diagnosed mainly during the course of three somatic illnesses: cancer, sciatica and hypertension, with respective rates of 90%, 85.7% and 60%.

The onset of a MDD during the evolution of a somatic disease was significantly more common in female patients (P=0.04) and those living in couple family (P=0.005).

Among all psychiatric disorders, depression and AD were the most frequently associated disorders with somatic diseases. This comorbidity may be explained by the physiological and psychological impact of certain somatic diseases, the iatrogenic effect of certain treatments, or the involvement of a biological, psychological or environmental common factor for both conditions.