Is cognition seasonal?

The idea that our mental life is more sluggish in winter is apparently seductive. This article reviews the evidence for the claim that there is a seasonal cycle in human cognition. Several methodologies have been used with participants such as over-wintering scientists in Antarctica, residents of polar regions, and patients with seasonal psychopathology and there is no clear tendency for cognition to be impaired in winter. Some large-scale public health studies report seasonality of cognition but are inconsistent regarding when in the year there is a peak and trough. Claims that human cognition has an annual cycle should be regarded as speculative and the burden of proof must be borne by anyone inclined to claim that such a cycle exists. An analysis of the influence of some key studies shows that their results are misleadingly cited and that there is resistance to the null conclusion.