In a recent Round the Corner, Mitchell commented on a Cochrane Review of exercise therapy for chronic fatigue syndrome (CFS). One of the trials included in that review, and discussed by Mitchell, was the PACE trial. In this month's Round the Corner we are publishing a response we received from authors of the PACE trial (Chalder, White & Sharpe), together with Mitchell's reply. Ed.

Revisions of international classification systems for mental disorders have focused on improving the reliability of diagnostic criteria. However, the uncertain validity of the current diagnostic categories means that they do not always fulfil their key purposes, namely to guide treatment and predict outcomes. This is especially true when traditional diagnostic approaches are applied to adolescents and young adults with emerging illnesses. A clinical staging model, similar to those used in general medicine, could improve diagnosis in psychiatry and aid treatment decision-making, especially if applied to individuals aged about 15–25 years, which is the peak age range for the onset of severe mental disorders. Staging models may offer a new framework for the development of interventions with high benefit and low risk, and for research into neurobiological and psychosocial risk factors. However, this approach is not without controversy: some experts oppose its introduction, some argue that it represents a transdiagnostic model, and some suggest it is only viable if disorder-specific models are used.

Therapy for sexual problems is not solely based on findings from scientific studies; much of it has to do with intuitive knowledge that comes from personal and clinical experience. The author suggests that an ideal way to begin education about helping with patients' sexual identity, sexual function and relational concerns is to consider why sex is important. Answering this question illuminates the subtle roles sexual behaviour play in our lives. These roles are explained by providing clinically based responses to twelve questions: How are adults nurtured in sexual relationships? How is psychological intimacy created? What is learnt over time through sex? What accounts for the pleasures of sex? Why is sex important? Why is sexual experience unstable? What is a couple's sexual equilibrium? What is sensuality? Is a life of sexual pleasure possible? What is sexual health? What are the sources of distress about sex? How do these concepts facilitate therapy?

There has been a resurgence of interest in the role of childhood trauma in the aetiology of psychosis. In this review, recent findings on the association between childhood trauma and a continuum of psychotic symptoms are presented. Evidence of the association between specific childhood trauma subtypes and psychotic symptoms is examined, with a brief discussion of some current hypotheses about the potential mechanisms underlying the associations that have been found. Some practice implications of these findings are also highlighted.

Coughlan & Cannon have provided an extremely useful review, highlighting the evidence for the association between childhood trauma and psychosis. This is relevant to those working with individuals with psychosis across all age ranges. This commentary discusses further some of the points raised, the complexity of the association and developmental aspects.

Coughlan & Cannon's article provides a helpful review of the current state of evidence regarding the connection between childhood trauma and psychotic-like symptoms. This commentary focuses on the clinical implications by noting that much of the data comes from studies in non-patient populations and to some extent depends on the underlying assumption of the continuum model of psychosis. I reconsider the presented data focusing purely on clinical diagnoses of psychosis, and consider the implications of the association between trauma and psychosis by looking at the evidence base for specific trauma-focused therapies in psychosis.

We review thought disorder in psychopathology, including how one can assess it clinically, useful psychometric measures and its clinical importance. In the final section we discuss how recent studies in neuropsychology and neuroimaging have helped understand the mechanisms of abnormal speech and languages in psychotic illnesses.

Functional near-infrared spectroscopy (fNIRS) has been used in healthcare and medical research for the past two decades. In particular, the use of fNIRS in academic and clinical psychiatry has increased rapidly owing to its advantages over other neuroimaging modalities. fNIRS is a tool that can potentially supplement clinical interviews and mental state examinations to establish a psychiatric diagnosis and monitor treatment progress. This article provides a review of the theoretical background of fNIRS, key principles of its applications in psychiatry and its limitations, and shares a vision of its future applicability in psychiatric research and clinical practice.

This overview considers causes of disordered eating, including eating disorders, in older people. Eating disorders are becoming more common in older adults and research has shown a related mortality of 21%. The wide range of medical and pharmacological causes of weight loss in older people means that eating disorders may go undetected, occurring insidiously and surreptitiously.

Several English prisons contain democratic therapeutic communities (TCs) for personality disordered offenders, and addiction TCs for serious substance misusers. This article describes how these are organised and comments on how they are specifically tailored and accredited for use in custodial settings. It also describes ‘psychologically informed planned environments’ (PIPEs), offender pathways for those with personality disorders and psychopathy which provide additional support for psychological treatment. It ends by explaining how ‘enabling environments’ are assessed, since these are now becoming widely adopted in prisons to reverse toxic environments – which affect staff, the prison and the outside world as well as the individual prisoner – and to counter negative learning found in custodial institutions.

The professional regulatory cases of the psychiatrist Dr Richard Pool and the neuropathologist Dr Waney Squier have given rise to concerns among expert psychiatric witnesses, and indeed medical experts in general. Here we restate the law on expert evidence with particular reference to the judgment of the Supreme Court in the case of Kennedy v Cordia. We emphasise that Pool does not change the law regarding ‘what is expertise’; in particular, the case does not establish restrictive, status-based tests governing the admissibility of expert evidence such as according to whether an expert psychiatric witness has undergone higher training, is on the specialist register as a specialist in a particular field or is a consultant. Rather, expertise continues to be legally defined in terms of a combination of qualification, knowledge and experience. Crucially, the test of medical expertise in legal proceedings is a legal test and not one determined within a medical paradigm.