Well-being and biological cost of family members affected by substance use disorder of others.

This cross-sectional study assessed the well-being of family members affected (AFMs) by substance use disorder (SUD) of other family members. Mental symptoms, social avoidance, and quality of life (QoL) were measured for 775 Chinese AFMs and 206 controls. Saliva from 65 AFMs and 31 controls was analyzed for cortisol, BDNF, proBDNF, and mRNA levels of BDNF and its receptors (TrkB, P75^NTR, Sortilin). AFMs had significantly higher SCL-90 scores (t = 3.45, p < 0.01) and lower SF-36 scores (t = -4.70, p < 0.01). Of AFMs, 22.1% exhibited mental symptoms. Social support partially mediated the relationship between exposure to SUD patients and mental symptoms (effect = 0.31, SE = 0.16; 95% CI [0.02, 0.67]). Positive coping (effect = 0.03, SE = 0.01; 95% CI [0.01, 0.05]) and social support (effect = 0.02, SE = 0.01; 95% CI [0.01, 0.04]) mediated the effect of exposure to family SUD on social avoidance; positive coping mediated the effect on QoL (effect = -3.03, SE = 0.72; 95% CI [-4.58, -1.75]). AFMs exhibited higher cortisol (t = 2.10, p < 0.05) and proBDNF (t = 2.39, p < 0.05) levels and increased mRNA expression of BDNF (t = 0.66, p < 0.05) and TrkB (t = 1.12, p < 0.05). Cortisol positively predicted mental symptoms, and proBDNF negatively predicted QoL. In China, AFMs of SUD have increased risk of mental health issues and reduced QoL, likely due to elevated cortisol and proBDNF levels. Positive coping and social support are critical to mitigate these negative effects.