Background: The aim of this study was to explore the co-morbidity between Major Depressive Disorder (MDD) and Schizophrenia (SZ) among a large number of patients describing their clinical characteristics and rate of prevalence.
Subjects and methods: A cohort-study was carried out on 396 patients affected by MDD and SZ who consecutively attended the Department of Psychiatry, Rumeilah Hospital in Qatar. We employed the World Health Organization - Composite International Diagnostic Interview (WHO-CIDI) and the Structured Clinical Interview for DSM-5 (SCID-5) for diagnoses. Patients were also grouped in MDD patients with and without co-morbid SZ (MDD vs MDD/SZ) for comparisons.
Results: A total of 396 subjects were interviewed. MDD patients with comorbid SZ (146(36.8%)) were 42.69±14.33 years old whereas MDD without SZ patients (250 (63.2%)) aged 41.59±13.59. Statistically significant differences between MDD with SZ patients and MDD without SZ patients were: higher BMI (Body Mass Index) (p=0.025), lower family income (p=0.004), higher rate of cigarette smoking (p<0.001), and higher level of consanguinity (p=0.023). Also, statistically significant differences were found in General Health Score (p=0.017), Clinical Global Impression-BD Score (p=0.042), duration of illnesses (p=0.003), and Global Assessment of Functioning (p=0.012). Rates of anxiety dimensions (e.g.: general anxiety, agoraphobia, somatisation, etc.), mood dimensions (e.g.: major depression, mania, oppositional defiant behaviour, Bipolar disorder), Attention Deficit Hyperactivity Disorder, psychotic and personality dimensions were higher among MDD with SZ patients than MDD without SZ.
Conclusion: This study confirms that MDD with SZ is a common comorbidity especially among patients reporting higher level of consanguinity. MDD/SZ comorbidity presents unfavourable clinical characteristics and higher levels of morbidity at rating scales.