Childhood maltreatment is a risk factor for the development of post-traumatic stress disorders and psychosis. However, the association between post-traumatic stress disorder (PTSD), including complex PTSD, and psychotic symptoms is unknown. We investigated whether the presence of PTSD and complex PTSD was associated with psychotic symptom severity within survivors of developmental trauma.

As part of the Investigating Mechanisms underlying Psychosis Associated with Childhood Trauma (IMPACT) study, from Aug 20, 2020, to Jan 24, 2021, and from Sept 9, 2022, to Feb 21, 2023, using study advertisement on online platforms we recruited adult (≥18 years) participants who had experienced developmental trauma without a psychiatric diagnosis in the UK and South Korea. We measured whether participants met diagnostic thresholds for PTSD and complex PTSD using the self-reported International Trauma Questionnaire, and psychotic symptoms using the self-reported Community Assessment of Psychic Experiences. We used linear regression, adjusting for sociodemographic variables such as age, sex, ethnicity, educational attainment, and socioeconomic status, to examine whether there was an association between PTSD and complex PTSD and psychotic symptoms. The study is registered in the UK (University College London Research Ethics Committee [14317/001] and the National Health Service Research Ethics Committee [22/YH/0096]) and South Korea (Institutional Review Board of Seoul National University Bundang Hospital [B-2011-648-306]), and is ongoing.

Of the 2675 participants who took part in the study, 1273 had experienced developmental trauma and were included in the study in the UK (n=475) and South Korea (n=798), comprising 422 (33%) men and 851 (67%) women with a mean age of 26·9 years (SD 6, range 18–40), mostly of White British (n=328) or South Korean (n=798) ethnicity. We found no significant association between PTSD and psychotic symptom severity (total severity β=–2·40 [SE 3·28], p=0·47), compared with participants who did not meet PTSD or complex PTSD caseness. We found a significant relationship between complex PTSD and psychotic symptom severity (total severity β=22·62 [SE 1·65], p<0·0001), including for positive (β=12·07 [SE 0·99], p<0·0001) and negative symptoms (β=10·5 [SE 0·95], p<0·0001), compared with participants who did not meet PTSD or complex PTSD caseness.

Health systems must assess individuals with previous developmental trauma for complex PTSD and treat those affected. These individuals should also be assessed for psychotic symptoms, and if necessary, preventative measures should be taken to reduce risk of conversion. Further work should assess whether treating complex PTSD modifies the risk of conversion to psychosis.

UKRI Future Leaders Fellowship, British Medical Association Margaret Temple Award for Schizophrenia Research, and the National Research Foundation of Korea—Korea Government.