The association between plasma ACTH levels and suicidal ideation severity in patients with major depressive disorder remained robust to adjustment for major confounders (adjusted for age, sex, education years, body mass index, smoking status, plasma CRP and PEth concentration (measuring chronic alcohol exposure), and antidepressant use) in the linear regression model (t = −2.71, p = 0.011), as well as additionally adjusting for depression severity (t = −2.99, p = 0.006). Here, CRP is linked to depressive symptom measurement.