Suicide risk could be proportional to SCN tau above a zero suicide risk set-point of 24.05 hours

Suicide is the 10th leading cause of death and varies seasonally, suggesting involvement of the suprachiasmatic nucleus (SCN) and photoperiod, which both modulate suicide risk and tau, the free-running period of the SCN. This study hypothesized that tau linearly scales suicide risk. The CDC’s 22-year monthly suicide data were fitted with non-linear/cosine curves; annual means m and amplitudes d were extracted; extant tau values were extracted from the literature. The 22-year average annual suicide rhythm was indistinguishable from a pure sinusoid with a late-spring peak, implicating the photoperiod and SCN. Highly correlated variables m and d implicated SCN tau as the proportional driver of both and yielded a zero tau-related suicide risk set-point = 24.05 hours, above which tau-related suicide risk increased proportionally. The population attributable fraction estimated that >73% of all USA suicides were theoretically preventable by reducing tau, which could be the main risk factor for suicide.