Another systematic review and meta‐analysis have revealed that serum BDNF significantly decreases in patients who are diagnosed with anxiety disorders including post‐traumatic stress disorder and obsessive compulsive disorder (Suliman et al., 2013), yet panic disorder, a type of anxiety disorder (Hülya Kök, 2020), was not assessed in their work. This evidence concerns the gene BDNF and obsessive-compulsive disorder.