Background: Increased occurrence of several physical conditions has been reported in patients with depressive disorders. Various physical conditions and depressive disorder have been reported in patients with mitochondrial disorders. The aim of this study was to investigate mitochondrial function in selected depressed patients in search of an aetiological or pathophysiological factor common to both depression and physical symptoms.
Methods: Muscle biopsy was performed in 28 patients with a lifetime prevalence of major depressive disorder (MDD), and at least three chronic physical conditions that have been reported to be common in depressive as well as in mitochondrial disorders. Morphologic and biochemical investigations including mitochondrial ATP production rate (MAPR) by the bioluminometric method, spectrophotometric analyses of mitochondrial enzymes, and long-PCR and Southern blot techniques to detect mitochondrial DNA (mtDNA) deletions were performed. The Karolinska Scales of Personality (KSP) with 15 scales assessing vulnerability to psychopathology was filled in by 21 patients.
Results: Decreases of MAPR and enzyme ratios were found in the patients in comparison with controls (P<0.01). Deletions of mtDNA assessed with long-PCR were more frequent in patients than in controls (chi-square test P<0.05). Correlations were found between MAPR and the KSP scales 'Somatic Anxiety', 'Psychasthenia', and 'Suspicion' (P<0.01).
Limitations: Results cannot be compared with previous studies, and cannot be generalized to all MDD patients. Individually matched controls were not available.
Conclusions: The results suggest that mitochondrial dysfunction is associated with vulnerability to psychopathology in this selected patient group.