Background:
Anxiety disorders are common, associated with significant burden of disease, and have high levels of treatment resistance. Low-dose ketamine has been extensively studied in treatment-resistant depression, with fewer reports in treatment-resistant anxiety disorders.

Aims:
This systematic review and meta-analysis collected efficacy, safety, and tolerability data for ketamine as a treatment for anxiety spectrum disorders.

Methods:
We conducted a systematic search for randomized controlled trials (RCTs) of acute ketamine treatment for patients with anxiety disorders. Open-label trials of ketamine maintenance therapy were also considered. Qualitative and, where possible, quantitative syntheses of findings were performed using Review Manager software (RevMan). Acute dose-response and maintenance treatment data were also collected.

Results:
There were six eligible acute RCTs – two in social anxiety disorder (SAD), three in post-traumatic stress disorder (PTSD), and one in obsessive-compulsive disorder (OCD). Four of the six showed significant improvement in anxiety rating scores in ketamine compared with control groups. Pooled analysis showed ketamine was associated with an increased likelihood of treatment response for SAD (odds ratio (OR): 28.94; 95% confidence interval [CI]: 3.45–242.57; p = 0.002) but not for PTSD (OR: 2.03; 95% CI: 0.67–6.15; p = 0.21). A dose-response profile was observed for ketamine and changes in SAD symptoms, with doses ⩾0.5 mg/kg associated with greater reduction in anxiety rating scores than lower doses. Ketamine maintenance therapy was associated with sustained anxiolytic effects and improved social and/or work functioning.