Surgical Site Infection After Primary Posterior Lumbar Fusion Increases the Risk of New-Onset Mental Health Disorders:

Study Design: Retrospective cohort study using the TriNetX Global Research Network. Objective: To evaluate whether surgical site infection (SSI) after primary posterior lumbar fusion (PLF) is associated with increased risk of developing new mental health disorders (MHDs) over short-term and long-term follow-up. Summary of Background Data: Surgical site infections affect up to 9% of patients undergoing spine surgery and are known to increase physical morbidity. However, the psychological impact of SSI is poorly understood. Although postoperative complications have been linked to new-onset MHDs in general surgical populations, the specific risk attributable to SSI in primary PLF patients remains unclear. Methods: Adult patients (≥18 yr) undergoing primary PLF were identified and stratified by the presence or absence of postoperative SSI. Patients with pre-existing MHDs were excluded. Propensity score matching was performed 1:1 based on age, sex, race and ethnicity, BMI, comorbidities, preoperative labs, nicotine use, and socioeconomic factors, yielding 1,859 matched pairs. New-onset diagnoses of depression, anxiety, and substance use disorder (SUD) were assessed at 30 days, 90 days, 6 months, 1 year, and 2 years, and risk ratios (RR) with 95% CIs were calculated using χ 2 testing and Kaplan-Meier methods. Results: At 30 days, anxiety was more common in the SSI cohort (RR 2.63, P =0.004), whereas depression and SUD were not significantly different (both P >0.05). By six months, depression (RR: 1.69, P =0.021), anxiety (RR: 1.97, P =0.001), and SUD (RR: 1.87, P =0.04) were all elevated in the SSI group. At one year, depression (RR: 1.64, P =0.013) and anxiety (RR: 1.41, P =0.046) remained significantly higher, whereas SUD was similar between cohorts (RR: 0.98, P =0.93). Conclusions: Postoperative SSI significantly increases the risk of long-term psychological morbidity emphasizing the need for early mental health screening and intervention after infection.