Perceived association of mood and symptom severity in adults with mitochondrial diseases.

Individuals with genetic mitochondrial diseases suffer from multisystem symptoms that vary in severity and over time, but the factors influencing disease manifestations are poorly understood. Based upon i) patient and family reports that stressful life events trigger or exacerbate symptoms, ii) biologically plausible pathways whereby psychological states and stress hormones influence mitochondrial energy transformation capacity, and iii) epidemiological literature linking traumatic/stressful life events and multiple neurologic disorders, we hypothesized that mitochondrial disease symptom severity may in part vary with daily mood. To examine patients' perception around potential psycho-biological mechanisms known to operate in other chronic illnesses, we administered the Stress, Health and Emotion Survey (SHES) to 70 adults with self-reported mitochondrial diseases. Participants rated how severe each of their symptom(s) was over the past year, separately for either 'good' (happy, calm) or 'bad' (stress, sad) emotional days. On average, patients reported that most symptoms were better on "good" emotional days (p < 0.0001) and worse on "bad" emotional days (p < 0.0001). Of the 29 symptoms assessed, 27 were associated with daily mood (p < 0.01). Some but not all symptoms were reported to be less or more severe on good and bad days, respectively, including fatigue, exercise intolerance, brain fog, and fine motor coordination (ps < 0.0001). These associative results suggest that on average individuals living with mitochondrial diseases perceive a connection between their mood and symptoms severity. These preliminary findings constitute an initial step towards developing more comprehensive models to understand the psychobiological factors that influence the course of mitochondrial diseases.