An increased frequency of psychiatric dysfunctions, including major depressive, anxiety, and obsessive-compulsive disorders, manifested in a cohort of 18 subjects with GCH1 deficiency, and reduced levels of 5-hydroxyindolacetic acid and 3-methoxy-4-hydroxyphenylglycol in cerebrospinal fluid have been shown [16], [17]. Here, GCH1 is linked to Anxiety.