Hallucinogen use and intimate partner violence: Prospective evidence consistent with protective effects among men with histories of problematic substance use

Hallucinogens — a heterogeneous class that includes classic psychedelics such as LSD and psilocybin as well as other substances like MDMA, ketamine, and DMT-containing preparations — are receiving renewed scientific attention for potential therapeutic effects on a range of psychological and behavioural problems. Previous work, including early clinical reports and more recent naturalistic and pilot studies, has suggested that hallucinogen experiences can produce lasting personality and behavioural change, and some large prospective work has linked hallucinogen use to reduced criminal recidivism. At the same time, the literature is inconsistent: some studies find no effect or even elevated risk, and findings vary across substances, populations, and outcome measures. Intimate partner violence (IPV) is a common and serious form of interpersonal violence that is related to externalising psychopathology and to substance use, yet the relationship between hallucinogen use and IPV has not been comprehensively evaluated. Walsh and colleagues set out to address this gap by conducting the first prospective examination of whether prior naturalistic hallucinogen use predicts subsequent arrest for IPV among a high‑risk sample of incarcerated men with lifetime substance use disorders. The primary hypothesis was that any lifetime hallucinogen use would be associated with a reduced likelihood of post‑release IPV arrest; a secondary, more conservative analysis examined presence of a DSM‑IV hallucinogen use disorder as an alternate index of exposure. The study tests these associations while considering established covariates such as psychopathy, problematic alcohol use, and ethnicity.

The study employed a prospective, naturalistic design. Participants were 302 male inmates aged 17–40 years serving sentences of one year or less at a county jail in Illinois. Eligibility required lifetime presence of at least one DSM‑IV substance use disorder; individuals on psychotropic medication or unable to read English were excluded. Mean age was 26.06 years (SD=6.68); ethnic composition was 45.70% European American, 40.73% African American, and 13.58% Latino American. Institutional review procedures and written informed consent were reported. Lifetime hallucinogen exposure was assessed during incarceration using the SCID‑I substance use disorder module and coded in two ways: a liberal index of any lifetime use and a conservative index of lifetime DSM‑IV hallucinogen use disorder (dependence or abuse criteria). Psychopathic personality was measured by trained raters using the Psychopathy Checklist‑Revised (PCL‑R), based on interview and institutional file review. Symptoms of alcohol and cannabis dependence were derived from the SCID‑I. Socioeconomic status (Hollingshead Index), years of education, and ethnicity (self‑report recorded in jail roster) were also recorded; covariates were selected for multivariable analyses only if they showed preliminary associations with both hallucinogen use and IPV. The outcome was arrest for an IPV‑related offence (domestic battery) after release, ascertained prospectively from the Law Enforcement Agencies Data System, which aggregates state and national criminal records. Time to event was measured in months from release to IPV arrest or to the end of follow‑up, with adjustment for any intervening periods of re‑incarceration for non‑IPV reasons. Mean follow‑up time was 82.24 months (range 39–118 months). Survival analyses used Cox regression to examine time from release to IPV recidivism, with parallel models run for the two hallucinogen indices and with and without covariates. Preliminary bivariate tests (ANOVA, chi‑square) identified candidate covariates. Significance was set at p<0.05.

Descriptive characteristics and exposure prevalence: All participants met the inclusion criterion of a lifetime substance use disorder. Prior violent charges (robbery, assault, murder, weapons, kidnapping, sex crimes other than indecent exposure) were present for 71.52% of the sample. Lifetime use of any hallucinogen was reported by 55.63% (n=168) of participants; among these users 86.90% (n=146) reported use of classic psychedelics (psilocybin, LSD, mescaline). Of those who used classic psychedelics, 44.52% (n=65) also reported use of atypical hallucinogens (MDMA, PCP, ketamine). A lifetime hallucinogen use disorder (abuse or dependence criteria) was identified in 13.09% (n=22) of hallucinogen users; nearly all (90.90%, n=20) of those meeting hallucinogen‑use‑disorder criteria had used classic psychedelics. All participants who met hallucinogen‑use‑disorder criteria also met lifetime criteria for at least one other substance use disorder. IPV outcomes and bivariate comparisons: Over follow‑up, 33.44% (n=101) of participants were arrested for IPV; the mean survival time for the full sample was 59.25 months (SE=1.73). In bivariate Cox analyses, any lifetime hallucinogen use was associated with lower rates of later IPV arrest: 26.79% of hallucinogen users were arrested for IPV (mean survival time=62.76 months, SE=2.25) compared with 41.79% of non‑users (mean survival time=54.85 months, SE=2.65). Preliminary analyses showed that hallucinogen users had more alcohol dependence symptoms and that European Americans were overrepresented among hallucinogen users. Individuals meeting criteria for a hallucinogen use disorder tended to be more often European American, had higher psychopathy scores, and reported more cannabis dependence symptoms. Adjusted analyses and supplementary results: Psychopathic personality (PCL‑R), alcohol dependence symptoms, and ethnicity met criteria for inclusion as covariates because they were associated with both exposure and outcome. In Cox regression models controlling for these covariates, lifetime hallucinogen use remained predictive of reduced risk of IPV arrest. Supplementary analyses using the conservative index (lifetime hallucinogen use disorder) produced a similar but weaker pattern: 13.64% of those with a lifetime hallucinogen use disorder were arrested for IPV (mean survival time=68.82 months, SE=3.49) compared with 35.00% of those without such a disorder (mean survival time=58.50 months, SE=1.84); the association for the disorder index was reported at trend level after covariate adjustment.

The investigators interpret their prospective findings as consistent with a protective association between prior hallucinogen use and subsequent arrest for IPV among incarcerated men with histories of substance use disorders. They note that the magnitude of the effect was substantial in pragmatic terms: lifetime hallucinogen users were substantially less likely to be arrested for IPV than non‑users, and those meeting criteria for a lifetime hallucinogen use disorder were even less likely, though analyses using the disorder index were weaker. Walsh and colleagues situate these results alongside previous prospective evidence of reduced criminal supervision failure among hallucinogen users and with reports of lasting personality and social‑behavioural changes following hallucinogen exposure, while acknowledging discrepant retrospective community‑sample findings that reported increased risk in a different study design. The authors emphasise important limitations that constrain causal inference and the specificity of interpretation. The naturalistic, prospective design cannot rule out unmeasured confounders that covary with both hallucinogen use and IPV (beyond the alcohol, cannabis, and psychopathy measures they included). Mechanisms remain speculative; the investigators suggest possible pathways such as downstream reductions in use of other violence‑provoking substances (for example alcohol) or psychosocial changes following mystical or empathogenic experiences, but note these were not directly measured. Measurement limitations included reliance on official arrest records for IPV (which undercount total IPV), retrospective interview assessment of lifetime hallucinogen use, measurement only of pre‑release use (so post‑release consumption patterns were unknown), and the common co‑use of classic and atypical hallucinogens which prevents attribution to a specific substance class. Generalisability is limited by the single‑institution, high‑polysubstance use sample. Given these caveats, the authors call for further longitudinal and mechanistic research, better temporal measurement of substance use and IPV, control for polysubstance use, and removal of research impediments to more rigorously evaluate therapeutic potential. They conclude that the findings add preliminary evidence that hallucinogens may be an exception to the typical positive association between substance use and criminal behaviour, and that this literature warrants further investigation rather than continued stigmatization of these substances.