When investigating the etiology of diseases, epidemiological observational studies traditionally deemphasize psychosomatic associations. Exploring cognitive behavior provides an insight into how psychosomatic associations affect disease. Yoga philosophy identifies the kleshas (mental afflictions) of ignorance, ego, desire, hatred, and fear of death with disease. This is because individuals' perceptions and beliefs generate and reflect streams of thought that may shape their behavior and manifest as, or predispose them to, particular disease(s). The present study takes a yogic philosophical perspective to help elucidate unexplored associations between thinking about different aspects of life and the severity of Parkinson's disease (PD). The study involved a cross-sectional sample survey. Parkinson's New Zealand selected a random sample of 990 of its members. A self-completed questionnaire was sent to them. It asked questions about how often, over the previous 4 weeks, they had thought about 18 aspects of life commonly associated with the kleshas. A completed questionnaire was returned by 319 people (32%). Respondents thought most about family (87%), health (64%), rest and sleep (57%), food (53%), and the future (52%). They reported thinking least about work (48%), sex (45%), death (42%), and being virtuous (39%). A weak, but hypothesized positive, association (r = 0.2, p < 0.000) was detected between PD severity and thinking about death. The study could not determine whether thinking about death was (1) a cause or consequence of PD severity, and (2) a premorbid behavior. However, the possibility that stress associated with thinking about death accelerates PD progression is consistent with yoga philosophy and with neurophysiological mechanisms associated with the psychosomatic connections. The findings are worthy of future testing. A retrospective cohort study and qualitative research could deepen understanding about the role of kleshas in PD.

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