The role of anti-glutamic acid decarboxylase autoantibodies in mood disorders

Gamma‐aminobutyric acid (GABA) possibly plays a causative role in mood disorders. This hypothesis originated with studies on the beneficial effect of valproate in mania and as a mood stabilizer. Since valproate is known for its action in increasing the level of GABA, it was indirectly suggested that decreasing levels of GABA were responsible for mood alterations. To identify factors causing the decreased levels of GABA, studies have concentrated on the activity of the enzyme L‐glutamic acid decarboxylase (GAD), which catalyzes the transformation of glutamate to GABA, as a decreasing function of this enzyme induces lower levels of the neurotransmitter. Moreover, a very limited amount of research investigated the possible role of glutamic acid decarboxylase antibodies (GADA) in determining a decreased enzymatic function of GAD. If these findings are confirmed, it will be possible to improve diagnosis and treatment of mood disorders. In addition, if the presence of GADA is associated with a genetic trait, this would allow and facilitate early diagnoses.