Objectives:
Mitochondrial disorders of energetic metabolism (MD) represent a heterogeneous group of diseases manifesting at any age with a broad spectrum of clinical symptoms, including psychiatric disorders.

Methods:
The aim of the study was to characterize psychiatric symptoms and diagnoses in five patients with MELAS syndrome between the ages of 17 and 53 year.

Results:
Four of MELAS patients them harbored the prevalent mitochondrial DNA (mtDNA) mutation 3243A>G, and one patient had the mtDNA mutation 12706T>C. Three patients had positive family histories for MELAS syndrome. In one patient, depression was diagnosed as the first symptom of MELAS syndrome. Depression also preceded a stroke-like episode in one patient. Four patients had disturbed cognitive functions, confusional states occurred in three patients. One patient manifested psychotic (schizophrenia-like) symptom.

Conclusions:
Mitochondrial disorders deserve consideration as part of the differential diagnosis, especially if there is suspected involvement of other organ groups or positive family history of MD.