It is to see the ‘big picture’ that I read psychiatric books – to see the wood despite the trees. Forests of the latter are felled to keep us abreast of new knowledge in the form of mostly ephemeral journal articles. By the ‘big picture’ I mean principles and assumptions: the methods we use to understand the subject matter, the key organising ideas, analyses of the contexts in which we practise (social, political and ethical), and so on.

There is a nice mix of international and local messages in this month's Journal. Nine contributions refer to the causes, features and treatment of depression, ranging from George Szmukler's (pp. 457–460) reminder of the importance of Brown and Harris' work on life events in depression, through studies showing that both prematurity and child sexual abuse may precipitate depression (Patton et al, pp. 446–447 and Spataro et al, pp. 416–421) and that alcohol use may lead to suicidal behaviour (McCloud et al, pp. 439–445), somatization as a depressive symptom (Okulate et al, pp. 422–427), and accounts of variation in depression and its associated burden both in the European Union and across the world (Marušiä, pp. 450–451; Crawford, pp. 379–380; üstün et al, pp. 386–392; and Chisholm et al, pp. 393–403). It is pleasing to report that none of these articles is weighed down by the undoubted burden of this highly prevalent condition; but although we now have clear ways of preventing and treating it, it is a matter of some concern that, hydra-like, it returns time and again in so many different forms. But although common factors are invariably present, local differences can tell us much, and Peet's (pp. 404–408) challenging thesis on diet as a cause of this variation in both depression and schizophrenia is bound to stimulate further enquiry, as indeed will the bothering evidence from Tolmac & Hodes (pp. 428–431) that adolescent psychotic disorder is more common in people from Black ethnic groups. The attraction of biological psychiatry is that local variation should not occur, and if Jensen et al (pp. 409–415) are correct that glycerophosphocholine levels are increased in the anterior cingulate gyrus in first-episode schizophrenia, this should be similar across the world. Or perhaps there might be variation, and that's when we go back to Peet's hypothesis.