Salivary cortisol trajectories among inpatients undergoing substance use disorder treatment: A prospective...

A growing body of research among inpatients with substance use disorders (SUD) suggests a link between cortisol levels and treatment outcomes. However, there is limited insight into the pattern of cortisol level during an inpatient SUD treatment stay.

The aim was to investigate changes in salivary cortisol levels during 8 weeks of an inpatient SUD treatment stay, and to determine whether the primary SUD diagnosis exerted a distinct effect on cortisol level trajectories.

We employed a prospective repeated-measures design and followed a cohort of patients with various SUD diagnoses. Salivary cortisol samples were collected at four time points during the first 8 weeks of the treatment stay (t1: week 2 (baseline); t2: week 4; t3: week 6; and t4: week 8). We assessed basal cortisol concentration by calculating the area under the curve with respect to ground (AUC_G), which represents total daily cortisol output. Associations were determined using Linear mixed model analyses (LMMs).

The analytic sample comprised 173 patients. The full LMM model, including covariates (i.e. polysubstance disorder, age, gender, treatment history, treatment unit, mental distress) revealed that cortisol levels decreased from t1 to t2 (β = -7.218; 95 % CI: -11.126 to -3.310; p < 0.001) and stabilized thereafter. Patients with opioid use disorders (OUD) had lower cortisol level trajectories than patients with stimulant use disorders (β=-20.357; 95 % CI: -29.394 to -11.319; p < 0.001), while patients treated in the long-term unit showed elevated cortisol trajectories relative to those in the short-term unit (β=6.650; 95 % CI: 0.072-13.229; p = 0.048).

This study showed a decline in cortisol levels during the first 4 weeks of SUD inpatient treatment, followed by stabilization. Patients with stimulant use disorders had higher cortisol levels over time than those with OUD. Further research should explore the clinical implications of the current findings. In particular, greater insight into the moderating effects of polysubstance disorders on cortisol levels may contribute to the development of individual tailored treatment approaches.