Anxiety and depression following cumulative low-level exposure to organophosphate pesticides

•This study explored the impact of low-level organophosphate (OP) exposure on mood.•Exposed participants reported more symptoms of anxiety and depression than controls.•This was only true when self-report measures were used (the BDI-II, BAI and HADS).•Exposure was only related to anxiety (not depression) when using clinical interviews.•Self-report measures may exaggerate the impact of OP exposure on mood.

Previous research suggests that individuals with a prior history of pesticide poisoning are at increased risk of psychiatric disorder (Freire and Koifman, 2013), but findings regarding the impact of cumulative low-level exposure are inconsistent. The aim of the current study was to investigate whether sheep farmers with a history of low-level exposure to organophosphate pesticides (1) report a higher level of psychological distress on subjective symptom questionnaires, compared to unexposed controls (2) also meet internationally agreed diagnostic criteria for a psychiatric disorder more often than unexposed controls. 127sheep farmers were evaluated and compared to 78 unexposed controls, matched in terms of gender, education, level of intelligence, working status and area of residence. Both self-report measures and structured clinical interviews were used to assess mental health. The exposed cohort reported significantly higher rates of anxiety and depression when self-report questionnaires were used to evaluate mood, even when stressful life events, demographic and physical health factors were taken into account. However, when diagnostic interviews were used to assess mood, this pattern only held true for anxiety.