Stress, Depression, and Purpose-Specific Use of Dietary Supplements and Over-the-Counter Preparations: A Cross-Sectional Study of 120,000 Polish Adults

Background/Objectives: Dietary supplements and over-the-counter (OTC) preparations are widely used to self-manage stress, low mood, and disturbed sleep. Population research has treated such use as one undifferentiated behaviour. We examined whether stress and affective burden co-occur with supplement and OTC use in a purpose-specific way and how they relate to self-medication and primary-care contact. Methods: We analysed cross-sectional data from the National Test of Poles’ Health (non-probability, self-selected web survey; wave 5, 2024; N = 120,000), with trend analyses across five cross-sections (2020–2024). Survey-weighted logistic regression related four indicators of psychological burden to purpose-specific use of mood-, sleep-, and memory-targeted products, with a symptom-by-purpose matrix, age- and sex-stratified replication, and E-values. Results: Mood-product use rose along a gradient of psychological burden, from frequent stress (adjusted odds ratios [aOR] 1.80, 95% confidence intervals [CI] 1.72–1.88) through work-related exhaustion (2.17, 2.08–2.26) and poor self-rated mental health (2.44, 2.34–2.55) to a lifetime depression diagnosis (2.53, 2.41–2.65). A lifetime depression diagnosis also co-occurred with sleep (1.92, 1.83–2.01) and memory-product use (1.77, 1.69–1.85), while multivitamin and hair/skin use stayed flat (aOR ≈ 1.0). In this subgroup (n = 21,793), targeted use co-occurred with OTC self-medication (mood 1.70, 1.59–1.83; sleep 1.61, 1.50–1.73) without reduced primary-care contact. Associations were observed in both broad age strata (≤54 vs. >54 years) and both sexes (E-values 4.3–9.5). Purpose-specific use rose across the five cross-sections. Conclusions: Supplement use tracks stress and affective burden in a purpose-specific way and, among respondents reporting a lifetime physician diagnosis of depression, accompanies OTC self-medication. This pattern marks a group whose self-management concentrates on preparations with limited trial support. The scope of these findings is set by two features: the depression measure is lifetime, not an assessment of current symptoms, and the questionnaire recorded the purpose of use, not the product identity, ingredients or dose.