Young's Schema Focused Therapy (SFT) is gaining popularity in the treatment of older adults. In the context of this therapy, the Young Schema Questionnaire (YSQ) was developed to assess the early maladaptive schemas (EMS). EMS are considered to be relatively stable over time, but research shows that questionnaires often lack face validity in older adults, which makes it difficult to investigate EMS in older adults and their stability across the lifespan.

In the present cross-sectional study, we investigated the age neutrality of the Young Schema Questionnaire – Long Form in young (aged 18–34 years), middle-aged (aged 35–59 years), and older (aged 60–75 years) adults in a clinical sample of substance use disorders (N = 321) by examining potential differential item functioning (DIF). While investigating the stability of the schemas, we controlled for substance dependency and clinical symptoms by means of, respectively, the Drug Use Screening Inventory – Revised and the Symptom Checklist-90-R.

The Bonferroni-adjusted Liu–Agresti Cumulative Common Log-Odds Ratio confirmed large DIF for six items, divided across five schema scales (Mistrust/Abuse, Subjugation, Entitlement, Enmeshment and Self-sacrifice). Of the six items that presented DIF, only one item showed differential test functioning (Entitlement). Overall results show only 3% DIF, implying age neutrality of the questionnaire.

Current results corroborate that most EMS scales are equally measured across age, and reliable comparisons can be made across the lifespan, allowing for good clinical practice and further research on SFT in older adults. Only for Entitlement, Enmeshment, and Insufficient Self-control, caution is needed when comparing mean scores across the age groups.