As bright February sunshine poured through my window, I thought how appropriate that I should be reading about seasonal affective disorder (SAD). We all know how such sunny spring days can lift the gloom induced by weeks of grey cloudy skies and the endless drizzle of a British winter. However, is there a deeper intensity of winter gloom and the need for earlier, brighter light for some — the sufferers of the relatively recently recognised, and aptly named, SAD? This seems to be the book to find out. As the title suggests, the book benefits from using a broad research base to back up its claims. I was also impressed by the comprehensive coverage, ranging from clinically oriented chapters on diagnosis and treatment to more academic discussions related to demographics and postulated aetiologies. The condition remains controversial but sceptics are likely to be reassured by the acknowledgement of limitations to existing research found in most chapters. Supporters of the condition would benefit from consideration of the chapter by Eastman outlining the evidence that a placebo effect of expectation might account for positive results in many trials of light-box therapy. They should also critically appraise the evidence for the psychometric properties of the Seasonal Pattern Adjustment Questionnaire, a retrospective self-report measure initially designed to screen for, but not diagnose, SAD and upon which much of the research into SAD relies. The sceptics will gain food for thought from the detailed evidence regarding symptom patterns, epidemiology, comorbidity and treatment.

Those of us who do not have ready access to light-boxes or who have missed the seasonal aspect of a depressive disorder, reported by the book to occur in at least 1 in 100 adults, will be reassured to know that although light-box therapy is recommended, selective serotonin reuptake inhibitors seem to be as effective in achieving recovery and advising patients to have a brief walk each morning may also help. The fact that one chapter recommends that patients browse at different light boxes in cafés prior to purchase suggests that Britain may be lagging behind other countries in public awareness of the disorder.

The book has a clear style and provides a broad but detailed introduction to SAD. I would recommend it to clinicians seeing people with depressive disorders and to researchers in the field. I would encourage all to keep an open mind to the evidence presented and to its critical appraisal.