Endocannabinoid System (ECS) has been highlighted as one of the most relevant research topics by neurobiologists, pharmacists, basic scientists and clinicians (Skaper and Di Marzo, 2012). Recent work has associated major depressive disorder with the ECS (Ashton and Moore, 2011). Despite the close relationship between depression and bipolar disorders, as far as we know, there is no characterization of ECS and congeners in a sample of patients with bipolar disorders.

The objective of this work is to characterize the plasma levels of endocannabinoids and congeners in a sample of patients with bipolar disorders.

The clinical group was composed by 19 patients with a diagnosis of bipolar disorders using SCID-IV (First et al., 1999). The control group was formed by 18 relatives of first- or second-degree of the patients.

The following endocannabinoids and congeners were quantified: N-palmitoleoylethanolamide (POEA), N-palmitolylethanolamide (PEA), N-oleoylethanolamide (OEA), N-stearoylethanolamide (SEA), N-arachidonoylethanolamide (AEA), N-dihomo-γ-linolenoylethanolamide (DGLEA), N-docosatetraenoylethanolamide (DEA), N-linoleoylethanolamide (LEA), N-docosahexaenoylethanolamide (DHEA), 2-arachidonoylglycerol (2-AG), 2-linoleoylglycerol (2-LG), and 2-oleoylglycerol (2-OG).

The result showed statistically significant lower levels of AEA, DEA and DHEA in clinical sample. Previous research also identified lower levels of AEA in depressed women (Hill et al., 2008, 2009). Until date, it is unknown if DEA and DHEA have some effect on EC receptors, and whether they have some direct effects on endocannabinoids.

It would be necessary to carry our other research with a larger sample, which could allow the control of potential confounding variables.

The authors have not supplied their declaration of competing interest.