This book has three stated aims. The authors present the theory behind chronobiological treatments for affective disorder, document evidence of their efficacy and provide a step-by-step guide to clinicians as to how these therapies might be implemented. My main criticism of the book is that the balance between these three areas may not be optimal.

Manuals should probably instruct readers in how to do something rather than explain in depth why they should do it. However, whereas the guide to the implementation of chronotherapeutic techniques is detailed, the theory underlying these techniques merits expansion and I felt that evidence for their effectiveness was significantly lacking. For example, the efficacy of bright light treatment for non-seasonal depression is affirmed in fewer than 100 words, with only two references. In some European countries, chronotherapeutics are quite widely used and in Milan it is apparently routine for in-patients on medication for non-seasonal depression to receive light therapy and a single session of late-night wake therapy at the start of treatment. By contrast, in the UK, the authors would be preaching chronotherapeutics to the unconverted; most psychiatric professionals will need to know why they are using a treatment, not least because they might be asked by the patient.

Despite these criticisms, I found the book to be useful and engaging. It is well written and elegantly illustrated and it links to an informative website (www.cet.org) for the Center for Environmental Therapeutics, a non-profit agency dedicated to education and research in environmental therapies. The difficulties inherent in researching and promoting such therapies, in contrast to the international resources of the pharmaceutical industry, are noteworthy.

Most psychiatrists will have patients with unipolar or bipolar depression who are resistant to other treatments and this book may help to see them, literally, in a different light. There is a very useful level of detail about light therapy, including ways of estimating the best time of day at which it can be prescribed, since this varies between individuals. Helpful illustrative schedules are given for using light therapy alone, wake therapy plus light therapy and wake therapy plus light therapy plus sleep phase advance. There are informative sections on the use of melatonin and the practicalities of light therapy, including recognition that motivated and knowledgeable night nurses are required to competently implement some of the chronotherapeutic techniques with in-patients.

Overall, I feel that clinicians who work with patients with affective disorders should gain new and significant insights from reading this book.