BackgroundLow levels of soluble TNF-like weak inducer of apoptosis (sTWEAK) have previously been linked to cardiovascular disease, which is also the case for depression. High levels of galectin-3 and HbA1c, and low levels of HDL-cholesterol, have previously been linked to depression in these patients. The aim was to explore whether low levels of sTWEAK were associated with depression in type 1 diabetes patients. We adjusted for age, sex, galectin-3, HbA1c, HDL-cholesterol, antidepressants, and cardiovascular complications. MethodsCross-sectional design. Type 1 diabetes patients (n=287, men 56%, age18-59 years) were consecutively recruited from one specialist diabetes out-patient clinic. Depression was defined as Hospital Anxiety and Depression Scale-Depression sub scale ≥8 points. Blood samples, anthropometrics and blood pressure were collected, supplemented with data from electronic medical records. ELISA was used to measure sTWEAK and galectin-3. Low sTWEAK was defined as <7.1 ng/ml (<70th percentile), high galectin-3 as ≥2.562 µg/l (≥85th percentile) and high HbA1c as >70 mmol/mol (>8.6%). Non-parametric tests were used. Multiple logistic regression analyses (Backward: Wald) were performed, and calibrated and validated for goodness of fit with the data variables. Results Median (q1, q3) (ng/ml) sTWEAK were for 30 depressed and 257 non-depressed patients 1.5 (1.2, 2.9) and 2.7 (1.3, 13.0) respectively (p =0.021); median (q1, q3) (µg/l) galectin-3 were 1.348 (0.827, 2.850) and 0.916 (0.533, 1.637) respectively (p = 0.005). Four-teen percent of patients with low sTWEAK were depressed, and 2% of patients with high sTWEAK were depressed (p = 0.003). Low sTWEAK (adjusted odds ratio (AOR) (CI)) 9.5 (2.0-46) ), high galectin-3 (AOR (CI) 6.5 (2.3-18.7)), use of antidepressants (AOR (CI) 10.3 (3.3-30.4)), HDL-cholesterol (per mmol/l) (inversely) (AOR (CI) 0.1 (0.03-0.5)), and age (per year) (AOR (CI) 1.05 (1.00-1.09)) were associated with depression. ConclusionsThe depressed patients with type 1 diabetes had lower levels of sTWEAK than the non-depressed, which might contribute to the increased risk for cardiovascular disease and mortality previously demonstrated in patients with depression. Low levels of sTWEAK and HDL-cholesterol and high levels of galectin-3 were independently associated with depression.