Introduction and objective:
Autism spectrum disorder (ASD) poses significant clinical, social, and economic challenges, affecting not only individuals diagnosed with the condition but also their families. Increasing evidence highlights a substantial psychosocial burden among caregivers, which may translate into broader societal and economic costs. The aim of this study was to assess the mental well-being of family members of individuals with ASD and to identify its determinants in relation to selected socio-demographic factors and time since diagnosis.

Material and methods:
A cross-sectional study was conducted in February 2025 among 310 adult family members of individuals diagnosed with ASD. Data were collected using the Computer-Assisted Web Interview (CAWI) method via the Ariadna Nationwide Research Panel. Mental well-being was measured using the WHO-5 Well-Being Index.

Results:
The findings revealed reduced mental well-being among respondents, with a median WHO-5 score of 44, and 57.74% of participants scoring below the threshold, indicating impaired well-being. No statistically significant differences were found in well-being depending on respondent gender (p = 0.124), gender of the family member with ASD (p = 0.539), or time since diagnosis (p = 0.113). Additionally, no significant interaction effects were observed in two-way ANOVA models.

Conclusions:
Reduced mental well-being appears to be a common and persistent feature among family members of individuals with ASD, independent of basic socio-demographic factors. The findings highlight the need for comprehensive, long-term support strategies addressing both psychological and socio-economic aspects of caregiving. From the perspective of health economics, improving caregiver well-being may contribute to reducing the indirect costs associated with ASD.