Craddock et al ^{Reference Craddock, Kerr and Thapar1} are to be congratulated for asking ‘What is the core expertise of the psychiatrist?’. In responding to this rhetorical question, they make reference to psychological and social factors in mental illness; yet the impression remains that they consider biomedical factors central to psychiatry and the others more peripheral. Why else, for example, do they refer to diagnosis but not case formulation in psychiatry?

Craddock et al attempt to identify the expertise of the psychiatrist without first defining the object of his or her expertise. If the nervous system is the object of the neurologist's expertise and the whole person/family is the object of the general practitioner's expertise, what is the object of the psychiatrist's expertise? For Ikkos et al ^{Reference Ikkos, Bouras, McQueen and St John-Smith2} this is affect. Affect refers to feelings, agitations and moods, which are manifested in consciousness, behaviour and relationships in family and society. It is disturbed affect that brings individuals to the attention of psychiatrists, whether voluntarily or not, especially when it cannot be contained in the family and primary care. Disturbed affect may be caused by neurological disease or functional impairment of the central nervous system, or by disturbed experience or relationships.

Elements of affect and its disturbance can be studied biologically because we share common evolutionary affective substrates with lower animals, including the basic emotions. ^{Reference Nesse, Stein, Kupfer and Schatzberg3} However, as we move from basic to higher emotions closer attention needs to be paid to social, cultural and psychological factors. Higher emotions depend on basic emotions. But higher emotions, in turn, influence basic emotions through the impact of ‘meaning’.

Meaning cannot be reduced to molecules. Different levels and models of explanation are required - a green piece of paper is not a dollar bill until social convention decrees so. Those engaged in its physical production and counterfeit surveillance need to understand the physical structure of the dollar but its major significance can only be understood at the level of meaning and social convention. Craddock et al's assertion that ‘any psychological explanation is, in principle, capable of being understood at the level of cellular function’ is embarrassingly naive for psychiatrists. Together with their statement that ‘psychology can be considered as a sub-branch of biology, in the same way that chemistry is a sub-branch of physics’ it is plainly wrong.

Psychiatry requires a broad understanding of human evolution. Behaviour narrowly defined by cellular biology is not sufficient. ^{Reference Nesse, Stein, Kupfer and Schatzberg3} Biology, ethology and paleoanthropology have shown that social living has been the most important recent evolutionary pressure for brain development. Emotions are the glue of social interactions; from the moment of birth we are instinctually driven to engage with others. The representation of affect states in self and other (mentalisation) is vital to affect regulation and effective social adaptation. Affect regulation and mentalisation are acquired through secure attachment relationships and contribute to emotional resilience, which help us to weather the challenges that life presents us with reduced risk of psychiatric illness.

The distinguished American developmental psychologist, Jerome Kagan, writes: ‘The influence of biology on human psychological functions is extensive but not unlimited. Evolutionary psychologists like to write that genes keep cultures “on a leash”. However culture, like a large powerful dog, can pull the person holding the leash to new, unplanned directions’ (p. 81). ^{Reference Kagan4} He also writes: ‘For reasons that are not obvious, British psychiatrists retain an interest in the psychological and sociological correlates of mental illness and have resisted a narrow biological perspective more effectively than their American counterparts’ (p. 53). ^{Reference Kagan4} Craddock et al's formulation threatens to take British psychiatry down the American cul-de-sac. Its reductionist outlook necessarily downgrades the importance of training and continuing professional development of psychiatrists in psychological, social and cultural matters to second place.

The history of the National Health Service has been fundamental in shaping British psychiatry today; it is an example of fundamental cultural influence. The relevance of psychosocial factors to the full range of mental disorders is well documented. ^{Reference Ikkos5} Psychiatry is a broad integrative specialty, with significant diversity within. Our core expertise is the management and not the elimination of the necessary tension between advances in biomedical science and a broader biopsychosocial model of practice. The broad biopsychosocial model is the only one consistent with the facts and not a compromise. A broad evolutionary perspective permits the examination of religion and spirituality as well as culture and society and their relevance to psychiatry.

In the context of the credit crunch British psychiatrists face renewed threats to add to old woes. Its enemies would like to caricature the specialty as limited and reductionist. Craddock et al give them further ammunition! However, Nesse ^{Reference Nesse, Stein, Kupfer and Schatzberg3} aptly captures the core expertise of psychiatrists when he writes (in this case specifically in relation to depression): ‘The clinical challenge is the same as it has always been - trying to understand people and their relationships, goals and feelings in order to understand, and help them understand, why they do what they do and why they feel what they feel. That, in combination with new diagnostic tests, genomic findings, and effective new drugs that block depression, will offer a bright future for treating depression’ (pp. 171-2).

The academic and professional leadership of psychiatrists should reflect the full range of our expertise.