The current study evaluated the effectiveness of intravenous ketamine treatment for suicidality in a community-based clinical sample of 295 outpatients (mean age= 40.37; 58.6 % male). We conducted growth mixture modeling to estimate latent classes of changes in symptoms of suicidality measured by the Concise Health Risk Tracking - Self-Report (CHRT-SR) across five infusions in a two-week course of treatment. Best-fit indices indicated three trajectory groups demonstrating non-linear, quadratic changes in CHRT-SR scores during ketamine treatment. The largest group of patients (n= 170, 57.6 %) had moderate CHRT-SR scores at baseline and showed gradual improvement during treatment. The other two groups of patients had severe CHRT-SR scores at baseline and diverged into one group with no improvement throughout treatment (n = 63, 21 %) and one group with rapid improvement (n = 62, 21 %). Of the clinical and demographic variables available and tested, only higher scores pertaining to active thoughts of death and/or plan were found to predict which of the patients with severe CHRT-SR scores at baseline would not benefit from treatment. The present study provides an important contribution to the knowledge of ketamine's effects on symptoms related to suicide over time. providing support for the possible effectiveness of ketamine in a proportion of patients.
Keywords: Community-based; Ketamine; Response trajectory; Suicide.
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