GABAergic and endocannabinoid dysfunction in anxiety - future therapeutic targets?

With a lifetime prevalence of up to 25% anxiety disorders are among the most frequently occurring psychiatric disorders. The etiology of anxiety is considered to be multifactorial with an interaction of neurobiological, psychological and environmental factors. With regard to neurobiological factors, several neurochemical systems and neuroanatomical circuits have been discussed to be involved. In particular, anxiety might be a result of insufficient inhibitory control, pointing towards a major role of the gamma-amino-butyric acid (GABA) system in these disorders. Preclinical and clinical studies discuss a decreased GABAergic inhibition in anxiety and patients with anxiety disorders. In view of these findings it is intriguing that benzodiazepines, which currently represent the most potent and powerful anxiolytic agents, act through an enhancement of GABAergic inhibition targeting the GABAA receptor. Thus, it has been suggested that the GABAergic system might represent a promising future target for new pharmacologic strategies for the treatment of anxiety. Closely linked to the GABAergic system is the endocannabinoid system, which might also play an important role in this group of disorders. The endocannabinoid system has particularly been involved in extinction learning, suggesting a key role of this system in the process of fear extinction. In this paper, both the GABAergic and the endocannabinoid system will be reviewed with regard to their role in anxiety and anxiety disorders in humans with particular attention to findings from genetic and neuroimaging studies. Moreover, both systems will be discussed as potential therapeutic targets.