Over the past 40 years, enormous progress has been made in psychotherapy research and there have been repeated demonstrations of positive effects for a range of psychological interventions, especially in the treatment of depression and anxiety disorders. ^{Reference Cuijpers, Sijbrandij, Koole, Huibers and Berking1,Reference Clarke, Mayo-Wilson, Kenny and Pilling2} However, the study of adverse effects has not received the same level of attention. ^{Reference Barlow3} This is despite the fact that even the earliest meta-analyses identified that, of nearly 500 outcomes studied, about 10% of the effect sizes were negative. ^{Reference Smith, Glass and Miller4,Reference Shapiro and Shapiro5} Therapists highlight that negative or adverse effects are seen in day-to-day practice; ^{Reference Castonguay, Boswell, Constantino, Goldfried and Hill6,Reference Nutt and Sharpe7} thus the case for systematically examining the adverse effects of psychotherapy would seem to be compelling.

It is unsurprising that psychotherapy can have negative outcomes; indeed, it simply indicates that psychological treatments are similar to almost every other therapeutic intervention used in medicine or mental health, from aspirin to brain surgery. ^{Reference Mohr8} However, what sets psychotherapies apart is that they are frequently recommended as the treatment of choice for a wide variety of patients, and often in preference to medications, because of the presumption that therapy will be helpful to all patients, or at the very least will not have any adverse effects. ^{Reference Nutt and Sharpe7,Reference Mohr8} This is in marked contrast to prevailing social and media representations of psychotropic medications. ^{Reference Nutt and Sharpe7}

One reason for the relative lack of scrutiny of therapies and the rigorous scrutiny of medications is the values that are brought to bear by three ‘interested parties’: society, the individual, and health professionals ^{Reference Strupp and Hadley9} . Increasingly, publications used to inform patient choice on available interventions for common mental disorders suggest that therapies and medications are equally efficacious, but that medications have side-effects, adverse effects or are addictive, whereas psychotherapy is nearly always portrayed with the absence of such issues. ^{Reference Nutt and Sharpe7}

Negative perceptions of medications are probably increased by regulatory requirements to identify drug harms as well as benefits in any scientific communications, and this feeds into the view that they are dangerous. The US Food and Drug Administration (FDA) requires side-effects or adverse effects to be listed alongside the benefits of a drug, and the UK regulators who undertake post- marketing surveillance of medications (the Committee on Safety of Medicines) amended the ‘yellow card’ scheme for reporting adverse effects of drugs, so that patients have been able to use them since about 2004. ^{Reference Nutt and Sharpe7} Although these strategies are entirely reasonable, no such systems or requirements are in place for therapies. ^{Reference Barlow3,Reference Nutt and Sharpe7}

One problem in trying to examine the issues of negative effects of psychological therapy is that the research approaches that are suitable for identifying positive effects often obscure negative effects, ^{Reference Barlow3,Reference Dimidjian and Hollon10,Reference Linden11} an issue that is compounded by the lack of a theoretical concept on how to define, classify and assess psychotherapy side-effects. ^{Reference Dimidjian and Hollon10,Reference Linden11} This does not mean that therapy researchers are complacent or negligent and indeed when problems have been identified changes in clinical practice have been instigated. One of the best examples is the transformation in perception of ‘critical incident stress debriefing’ (CISD), which was used routinely to help people immediately after a traumatic event. Over time it became apparent that significant subgroups of people who were treated with CISD actually experienced deterioration rather than an improvement in their psychological well-being, leading to changes in clinical guideline recommendations. ^{Reference Lilienfeld12} However, in the absence of empirical predictors of likely adverse effects of therapy, placing a greater emphasis on clinical monitoring may provide a means to better understand the causes of negative or iatrogenic effects and to differentiate them from lack of therapeutic efficacy or from short-lived (but distressing) therapy side-effects. ^{Reference Barlow3}

In the paper by Crawford et al, ^{Reference Crawford, Thana, Farquharson, Palmer, Hancock and Bassett13} about 1 in 20 adults offered therapies via the National Health Service or Improving Access to Psychological Therapies reported negative effects. Younger adults, individuals from minority ethnic groups (especially from Black, Asian and Chinese populations) and ‘non-heterosexuals’ (from lesbian, gay, bisexual, trans-sexual and transgender populations) were up to three times more likely to report negative effects than other individuals; unfortunately, other characteristics that can predict negative experiences, such as education and income, ^{Reference Lambert and Barley14} were not examined. In terms of types of therapy, self-reported rates of negative effects ranged from 4% for cognitive–behavioural therapy to 9% for psychodynamic therapy. Number of therapy sessions did not predict negative effects, but insufficient information about the nature of the therapy or rationale for the interventions was associated with negative experiences of therapy.

Crawford and colleagues go to some lengths to differentiate negative effects from side-effects or lack of efficacy, but the survey did not examine whether any therapist characteristics contributed to the patients' negative experiences of therapy. For example, it is known that therapeutic alliance consistently predicts satisfaction with the relationship and with clinical outcome, and also that patients who report negative effects are often seen by therapists who are slow to recognise the severity of the patients' disturbance and their magnitude of need. ^{Reference Scott15} This is important, as it is clear that expertise (i.e. clinical skilfulness in delivering the therapy) rather than experience (years of practicing a therapy) can make a critical difference to a patient's experience. ^{Reference Imel, Baldwin, Atkins, Owen, Baardseth and Wampold16} Also, several studies high-light that the general competence of a therapist is not synonymous with either their cultural competence ^{Reference Owen, Drinane, Tao, Adelson, Hook and Davis17,Reference Campos and Goldfried18} or level of comfort in discussing sexuality. ^{Reference Harris and Hays19,Reference McHugh, Whitton, Peckham, Welge and Otto20}