This editorial introduces the BJPsych Advances special issue on biological psychiatry.

This editorial introduces the second of two special issues of BJPsych Advances on neurodevelopmental disorders, including intellectual disability, autism spectrum disorder, attention-deficit hyperactivity disorder and epilepsy. Topics discussed in the issue include using technological advances such as apps to manage epilepsy in intellectual disability, person-centred support and integrated care, training, and non-restrictive approaches and appropriate medication for managing self-injurious and challenging behaviour.

The diagnosis of dementia poses several challenges, as a consequence of which the condition has been widely reported to be underdiagnosed in the general population. Currently, there is no single diagnostic test for dementia and the clinical judgement of primary care physicians is therefore a key determinant in identifying which patients are referred to specialist services for further assessment. This month's Cochrane Corner review found that the clinical judgement of general practitioners is more specific (58–99%) than sensitive (34–91%) in diagnosing dementia, although the data were limited by small sample size and significant heterogeneity. This commentary provides a critical appraisal of this systematic review and attempts to extrapolate conclusions relevant to current clinical practice, including potential areas of further research, to facilitate appropriate and timely referral of patients with suspected dementia to specialist services.

A ‘control’ provides a point of clinical comparison for a new intervention, allowing researchers and clinicians to draw more confident conclusions about the effectiveness or potential harm of a given, often novel, therapy. Although this aspect of a trial's design provides the basis from which interventional impact is measured, it is often less closely examined. This commentary appraises a Cochrane Review that compares various controls in common use in modern psychiatric research and aims to characterise their effects on the outcomes of that research.

Post-traumatic stress disorder is a disabling condition resulting from a range of traumas and affecting many people worldwide. This month's Cochrane Corner review systematically searched and reported findings from 66 randomised controlled trials of pharmacotherapy for PTSD, 54 of which were included in a meta-analysis. Evidence was shown for the benefit of selective serotonin reuptake inhibitors, mirtazapine and amitriptyline in treatment response. This Round the Corner commentary critically appraises the review's findings, concluding that the summative evidence was of poor quality owing to the low number of studies, the high risk of bias and significant heterogeneity.

Agitation and psychosis are two common distressing symptoms of dementia. The results of this issue's Cochrane Corner review suggest that, if a pharmacological approach is required, the use of risperidone and other atypical antipsychotics for the purpose of managing these symptoms seems questionable. Furthermore, typical antipsychotics, haloperidol in particular, might have a greater impact on agitation and psychosis than already recognised. This commentary critically appraises the evidence on the efficacy of typical and atypical antipsychotics for agitation and psychosis in dementia.

There is a debate in psychiatry regarding whether it is better to use neo-Kraepelinian diagnostic categories or unitary models of psychosis in clinical practice. This article argues that clinicians should use either model as appropriate for the case in question, along with the conceptual framework used in the clinical management of psychosis without a clear biological cause. It first explores the values involved in the development of psychiatric classification systems, the purpose of classification and how we reached the current DSM/ICD and unitary models of psychosis. It then describes a diagnostic approach in which the choice of model should depend on the case in question, and offers a diagnostic protocol to guide the decision.

Depression has a large socioeconomic burden, affecting an estimated 280 million people worldwide. Up to 55% remain symptomatic following pharmacological and psychological treatment and may be classified as having treatment-resistant depression. This commentary assesses two treatment options for this group – electroconvulsive therapy (ECT) and a novel approach, magnetic seizure therapy (MST) – with reference to a Cochrane Review comparing the two. The Cochrane analysis showed no clear benefit for MST, but the evidence is currently insufficient to draw firm conclusions.