Impact of seasonality on conducting clinical studies in dermatology.

It is generally accepted among dermatologists that certain skin diseases are subject to seasonal influence. This belief, however, is based primarily on anecdotal observation rather than fact-based evidence. To address this controversy, we performed a retrospective analysis of a total of 3931 subjects enrolled in 7 phase 3 clinical trials across the diseases acne, atopic dermatitis, and seborrheic dermatitis and found a seasonal effect to exist in the treatment response of the 3 very common dermatologic diseases studied. To be truly representative of a drug's benefit when the disease is known to be impacted by seasonality, efficacy figures in the package insert should therefore be based on data collected from patients enrolled across all seasons.