2.4. Covariates

Sex, age, education level (continuous, in years), BMI (in kg/m²), and current smoking status (yes vs no) were assessed as part of the baseline interview in NESDA. Level of physical activity was calculated using the total Metabolic Equivalent of Task (MET) score derived from the International Physical Activity Questionnaire (IPAQ).⁴² The number of alcoholic drinks consumed per week was calculated based on the Alcohol Use Disorders Identification Test.⁴³ The number of self‐reported chronic somatic diseases included heart diseases, diabetes mellitus, thyroid gland disease, arthritis or arthrosis, rheumatism, intestinal disorders, liver disease, cancer, neurological conditions and allergies. Medication use was based on drug container inspection of all medications used in the past month, classified according to the World Health Organization Anatomical Therapeutic Chemical (ATC) classification.⁴⁴ The use of treatment for elevated lipid levels and reduced HDL cholesterol levels (ATC: C10) were documented. Use of antidepressant medication was assessed. We distinguished three classes of antidepressants: selective serotonin reuptake inhibitors (SSRI; ATC: N06AB), tricyclic antidepressants (TCA; ATC: N06AA), and other antidepressants (ATC: N06AX). Finally, overnight fasting status (yes/no) at time of blood withdrawal was documented.