A comparative study of picolinic acid levels in patients of severe depression with and without suicidality

Background an Aim: Picolinic acid (PIC) is a metabolite of the kynurenine pathway, which is involved in the degradation of tryptophan, an essential amino acid. PIC has been suggested to have neuroprotective effects by inhibiting the production of quinolinic acid, a neurotoxic agent that can induce inflammation and oxidative stress in the brain. Several studies have reported the altered levels of PIC and other kynurenine metabolites in patients with suicidal behavior, indicating a possible link between PIC and suicide risk. However, the exact role of PIC in the pathophysiology of suicide is not fully understood and requires further investigation. We aim to assess the levels of PIC in patients with severe depression with and without suicidal attempts. Materials and Methods: A cross-sectional, observation study was conducted at MGM Medical College, Indore. The study consisted of two groups: Group A including patients of depression with suicidal attempt(s) and Group B including patients of depression without any suicidal attempt. After obtaining written informed consent, recruitment of the subjects was done as per strict inclusion criteria and exclusion criteria. Sociodemographic parameters such as age, gender, residence, and marital status were collected along with the clinical parameters such as Hamilton depression rating scale (HAM-D), Suicidal Behavior Questionnaire Revised (SBQ-R) score, and Beck Scale for suicidal ideation (BSSI). Blood samples of both the groups were measured for serum PIC using an auto analyzer. Results: Serum PIC levels were significantly lower (124.33 ± 51.15 ng/L) in the depression with suicidal attempt group than depression without suicide attempt which was 163 ± 41.28 ng/L (P < 0.01). SBQ-R, BSSI score, and number of suicide attempts correlated negatively with serum PIC levels. Conclusion: The depression with suicidal attempt(s) group has shown lower mean serum PIC levels than the depression without suicidal attempt(s) group, which was statistically significant. This indicates serum PIC could be a marker in severe depression.