Anxiety disorders are common, and cognitive–behavioural therapy (CBT) is a first-line treatment. Candidate gene studies have suggested a genetic basis to treatment response, but findings have been inconsistent.

To perform the first genome-wide association study (GWAS) of psychological treatment response in children with anxiety disorders (n = 980).

Presence and severity of anxiety was assessed using semi-structured interview at baseline, on completion of treatment (post-treatment), and 3 to 12 months after treatment completion (follow-up). DNA was genotyped using the Illumina Human Core Exome-12v1.0 array. Linear mixed models were used to test associations between genetic variants and response (change in symptom severity) immediately post-treatment and at 6-month follow-up.

No variants passed a genome-wide significance threshold (P=5×10–8) in either analysis. Four variants met criteria for suggestive significance (P<5×10–6) in association with response post-treatment, and three variants in the 6-month follow-up analysis.

This is the first genome-wide therapygenetic study. It suggests no common variants of very high effect underlie response to CBT. Future investigations should maximise power to detect single-variant and polygenic effects by using larger, more homogeneous cohorts.

We previously reported an association between 5HTTLPR genotype and outcome following cognitive–behavioural therapy (CBT) in child anxiety (Cohort 1). Children homozygous for the low-expression short-allele showed more positive outcomes. Other similar studies have produced mixed results, with most reporting no association between genotype and CBT outcome.

To replicate the association between 5HTTLPR and CBT outcome in child anxiety from the Genes for Treatment study (GxT Cohort 2, n = 829).

Logistic and linear mixed effects models were used to examine the relationship between 5HTTLPR and CBT outcomes. Mega-analyses using both cohorts were performed.

There was no significant effect of 5HTTLPR on CBT outcomes in Cohort 2. Mega-analyses identified a significant association between 5HTTLPR and remission from all anxiety disorders at follow-up (odds ratio 0.45, P = 0.014), but not primary anxiety disorder outcomes.

The association between 5HTTLPR genotype and CBT outcome did not replicate. Short-allele homozygotes showed more positive treatment outcomes, but with small, non-significant effects. Future studies would benefit from utilising whole genome approaches and large, homogenous samples.

Promising evidence has emerged of clinical gains using guided self-help cognitive–behavioural therapy (CBT) for child anxiety and by involving parents in treatment; however, the efficacy of guided parent-delivered CBT has not been systematically evaluated in UK primary and secondary settings.

To evaluate the efficacy of low-intensity guided parent-delivered CBT treatments for children with anxiety disorders.

A total of 194 children presenting with a current anxiety disorder, whose primary carer did not meet criteria for a current anxiety disorder, were randomly allocated to full guided parent-delivered CBT (four face-to-face and four telephone sessions) or brief guided parent-delivered CBT (two face-to-face and two telephone sessions), or a wait-list control group (trial registration: ISRCTN92977593). Presence and severity of child primary anxiety disorder (Anxiety Disorders Interview Schedule for DSM-IV, child/parent versions), improvement in child presentation of anxiety (Clinical Global Impression –Improvement scale), and change in child anxiety symptoms (Spence Children's Anxiety Scale, child/parent version and Child Anxiety Impact scale, parent version) were assessed at post-treatment and for those in the two active treatment groups, 6 months post-treatment.

Full guided parent-delivered CBT produced superior diagnostic outcomes compared with wait-list at post-treatment, whereas brief guided parent-delivered CBT did not: at post-treatment, 25 (50%) of those in the full guided CBT group had recovered from their primary diagnosis, compared with 16 (25%) of those on the wait-list (relative risk (RR) 1.85, 95% CI 1.14–2.99); and in the brief guided CBT group, 18 participants (39%) had recovered from their primary diagnosis post-treatment (RR = 1.56, 95% CI 0.89–2.74). Level of therapist training and experience was unrelated to child outcome.

Full guided parent-delivered CBT is an effective and inexpensive first-line treatment for child anxiety.