Aim of the study:
The study aimed to evaluate the effectiveness of a short-term existential intervention - 4FM Acceptance Training - delivered in an inpatient psychiatric setting. Grounded in the theory of the Four Fundamental Motivations (4FM), the intervention supports recovery and inner reorientation by strengthening basic existential capacities that constitute meaningful human existence. In addition, the study examined the prevalence of Complex PTSD (ICD-11), types of traumatic experiences (TEC), attachment styles (ASQ), and the diagnostic overlap between ICD-10 personality disorders and ICD-11 PTSD/CPTSD classifications.

Subject or material and methods:
Participants (N=32) hospitalized in a psychiatric ward were allocated to two groups: the experimental group received the 4FM intervention alongside standard treatment (TAU), while the control group received TAU only. The outcomes were assessed before and after the intervention (T0–T1), based on self-report questionnaires (PSWQ, CESD-R, SE, BHI-R). Additionally, trauma history (TEC) and ICD-10/ICD-11 psychiatric diagnoses were explored.

Results:
Participants in the intervention group demonstrated a significantly greater increase in Basic Hope compared to the TAU group (t(15) = –5.16, p < .001). No statistically significant changes were observed in anxiety, depression, or sense of fulfilment. Notably, 100% of participants reported emotional abuse, and 96.9% reported emotional neglect. The observed increase in Basic Hope occurred despite these widespread trauma histories. No significant differences were found between ICD-10 (F60/F61) and ICD-11 trauma-related diagnoses (PTSD/CPTSD), indicating a diagnostic overlap.

Discussion:
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Conclusions:
These findings highlight the potential of short-term, existentially grounded interventions to complement standard psychiatric care, particularly in populations with complex trauma and comorbid diagnoses. Future studies should explore long-term effects and scalability.