Trauma and Substance Misuse: Charting Heterogeneity in Comorbidity Dynamics, Vulnerable Populations, and Treatment Adaptation

Traumatic experiences are highly prevalent worldwide and known to have a range of biopsychosocial implications yielding dramatic, case-specific diversity in clinical presentations and outcomes. Just as there are many sources of trauma, people experiencing identical traumatic events have many different reactions, with only a subset reporting emergent trauma symptoms that develop into post-traumatic stress disorder (PTSD). Subclinical trauma symptoms and PTSD pose risk for chronic and pervasive challenges across numerous psychological and functional domains (e.g., emotion-regulation, substance use, social relationships, and educational attainment and employment) that also vary widely from person-to-person. Even in cases when the same set of hallmark symptoms are endorsed following exposure to a trauma, these trauma symptoms may in turn track with a wide range of impacts: some cases exhibit limited functional disruption followed by rapid remission of symptoms and progression to full recovery without intervention, whereas others are characterized by cascading and accumulating consequences and comorbidities conferring additional case complexity, clinical burden, and unmet treatment need.

One common co-occurrence that amplifies person-to-person heterogeneity in trauma is substance misuse. Trauma is tied to substance misuse via a purported bidirectional link wherein changes in one alter the dynamics and prognosis of the other over time. As with trauma experiences, substance use behavior and problems stemming from misuse exhibit profound variability across individuals and time in their acute manifestations (e.g., drug of choice, co-use or polysubstance use behavior, tonic and phasic craving patterns) and their proximal antecedents, trajectory of use patterns over time (e.g., sequence of onset/relapse, escalation, severity, and chronicity), and resultant consequences within and between people. Preexisting factors that vary from person-to-person may determine whether and how trauma and substance misuse co-occur. The persistence of their comorbidity may further undermine broader functioning at different rates for different people, leading to population-level variability in rates of effective screening, diagnosis, and treatment.

Individuals experiencing comorbid trauma symptoms and substance misuse may have profound differences in clinical needs. Thus, in order to actualize the benefits of precision psychiatry for dual diagnosis, research that characterizes and hones effective adaptive strategies for addressing clinical heterogeneity in the context of integrative intervention is needed. With this in mind, there are numerous unanswered questions involving heterogeneity that are especially pressing for researchers and health service providers—these include but are not limited to:

• Which sources and amounts of trauma exposure spur substance misuse onset, escalation, severity, and chronicity?

• What reactions to trauma increase likelihood of substance misuse (and vice versa)?

• Who is most vulnerable to substance misuse following trauma exposure (and vice versa)?

• What contexts are likely to increase risk for trauma and substance use comorbidity?

• Who should be screened, and when, for trauma exposure and substance misuse across contexts?

• What approach to screening should be used, and with whom, to ensure early identification of trauma symptoms and/or substance misuse and the potential for their comorbidity?

• Which treatment integrations and adaptations would be most accessible and beneficial for implementation by which clinicians and for which patients?

Two-part special issue of the Journal of Dual Diagnosis

In an attempt to aid progress in answering the questions listed above, the Journal of Dual Diagnosis is publishing a two-part Special Issue covering trauma and substance misuse. In the first of these consecutive Special Issues, papers collected here reflect shared consideration of heterogeneity at the intersection of trauma and substance misuse in three general areas: (1) person-to-person variation in dynamics between comorbid trauma and substance misuse, (2) risk levels across vulnerable subpopulations, and (3) considerations in the treatment of trauma symptoms comorbid with substance use disorder.

Person-to-person variation in dynamics between comorbid trauma and substance misuse

In service of discerning heterogeneity in which sources and amounts of trauma exposure spur substance misuse onset and prognosis, Jegede et al. (2023) present a report in this issue that uses open data from the National Epidemiologic Survey on Alcohol and Related Conditions to identify monotonic risk increases for substance use disorder (SUD) and multi-SUD accumulation across severity continuum groups for trauma sequelae (e.g., groups with no trauma exposure, trauma exposure but no PTSD, remitted PTSD, and current PTSD). Even in the absence of remitted or current PTSD, more than one traumatic experience heightened risk for SUD co-occurrence. Consequently, research studies and systems of care basing eligibility decisions (e.g., for treatment) on diagnostic criteria alone may be systematically omitting individuals at high risk for future SUD onset due to their subclinical trauma diagnostic status. Without careful attention to divergency in the co-morbid dynamics between the conditions, it is likely that high SUD risk may go unidentified at the time of PTSD screening, even in the absence of ostensible substance misuse. Research attending to this type of heterogeneity in risk across the dimensional continuum of trauma maximizes opportunity to identify who would benefit from referral and early intervention targeting SUD following trauma experiences.

Ferrie et al. (2023) additionally report results from a mediational test that investigated heterogeneity in what reactions to trauma increase likelihood of substance misuse. Specifically, they determined that drinking to cope with PTSD symptoms—as distinct from drinking to cope more broadly—accounts for the link between PTSD symptom severity and how often but not how much a given individual drinks. While not all people diagnosed with PTSD report strong motives to drink to cope with PTSD symptoms, Ferrie et al. (2023) note that those who do may benefit from orientation to protective behavioral strategies; but such approaches may only buffer frequency of alcohol drinking rather than hazardous quantities of alcohol consumption.

Heterogeneity in risk across vulnerable subpopulations

Also in this issue are three papers that explore questions of heterogeneity regarding (1) who is most vulnerable and (2) what contexts catalyze risk for trauma and substance misuse comorbidity. Work conducted by Beck et al. (2023) test whether drinking to cope motives for alcohol use account for variability in trauma and internalizing distress among nurses during the height of the COVID-19 pandemic. Beck et al. (2023) observe especially high rates of trauma exposure, alcohol misuse, and motives of drinking to cope in this population. While coping motives for drinking were prominent among nurses who were also experiencing more mental health symptoms (e.g., depression and PTSD) during this period, this variability did not additively account for levels of alcohol consumption. That is, despite ostensible and well-documented profession-specific and context-specific increases in vulnerability to increased drinking, trauma symptoms, and other mental health problems, none appear to be pathways for clinical problems for this group and context. Leonard et al. (2023) extend exploration of factors that account for variation in motives for alcohol use among a sample of firefighters, a group also at elevated risk for trauma symptoms and PTSD. Characterizing heterogeneity in the link between trauma and substance misuse in this vulnerable subpopulation, Leonard et al. (2023) investigated the extent to which variation in emotion regulation difficulties accounted for the link between self-reported PTSD symptom severity and alcohol use and problem severity. Emotion regulation was instrumental in accounting for the link between PTSD symptom severity and coping alcohol use motives but not other alcohol related motives (e.g., enhancement, conformity or social motives) or problems. Unique effects of coping motives for drinking across studies Beck et al. (2023) and Leonard et al. (2023) conducted in different populations signal the extent to which risks (e.g., self-medication motives) may operate in heterogeneous ways across individuals as a function of other contingencies that differentiate their experiences.

Also in this issue, North & Pfefferbaum (2023) investigate rates of substance use including tobacco and other substances in the years before and after exposure to 9/11 trauma among those who were present during the event. Authors highlight the especially diverse set of experiences under the purview of 9/11 trauma or 9/11-related PTSD based on the person’s location during the event, whether they were injured, and the extent to which the World Trade Center was a common location they visited (e.g., worked for a business located in the towers). Even as 35% of the sample endorsed 9/11-related PTSD following the event, rates of new onset of SUD were generally low and tobacco or other substance use did not appear to increase systematically across the sample, beyond those with a preexisting SUD. North & Pfefferbaum (2023) additionally consider issues of heterogeneity regarding who should be screened for substance misuse and when following trauma exposure. Given the absence of a common SUD outcome across cases of 9/11 trauma and preexisting SUD, authors discuss whether universal post-disaster screening would be beneficial given the high likelihood of low yield for preventing and/or identifying new cases of SUD. Instead, they argue that it may be optimal to consider disasters an opportune moment for widespread delivery of public health messaging and support for substance misuse.

Considerations in the treatment of trauma and substance use diagnoses

Heterogeneity poses unique challenges for consistently delivering effective treatment across cases. Evidence-based interventions designed for dual diagnosis are primarily validated in intentionally homogenous populations (e.g., meeting full diagnostic criteria for PTSD and alcohol use disorder only) that may be undermined at different rates across distinct profiles and sequelae of relevant comorbid trauma and substance misuse symptoms. Ware et al. (2023) highlight the need for gender-centered care as they chart gender-specific variation in the patterns of mental health risk aggregation that increase odds for high-risk substance use. Specifically, multiple mental health diagnoses elevated substance use risk to a greater degree in men than women, suggesting there is need to consider how the downstream treatment needs of men and women likely differ across a wide variety of diagnostic manifestations of the trauma and SUD comorbidity spectrum.

Given their awareness of the full spectrum of patient needs, clinicians are often tasked with adapting treatment to ensure that aspects of heterogeneity are addressed when evidence-based treatments fall short of providing a clear path for case-to-case adaptation. To that end, the report presented by Vujanovic et al. (2023) details results of an anonymous survey of clinicians querying their practices and preferences for implementation and integration. Even as a well-validated integrated treatment for PTSD and SUD exists (i.e., COPE; Back et al., 2014), clinicians report preferring an alternative PTSD intervention protocol (i.e., cognitive processing therapy) given its perceived pragmatic benefits across a wide variety of therapeutic contexts and patient characteristics. In order to ensure optimal treatment outcomes across individuals with psychiatric comorbidities, it is critical that the variable array of patient needs and clinician preferences be supported by a diversification of therapeutic approaches that would support enhancement of provider and patient choices.

Conclusion

Heterogeneity in trauma and substance misuse comorbidity may present an especially challenging barrier for uniformly meeting the needs of all individuals reporting these experiences and presenting for care. Many unique clinical presentations involved in their co-occurrence pose critical challenges for identifying risks and early clinical warning signs for each and effectively meeting the treatment needs across risks, symptoms, and consequences of both conditions to support remission and prevent relapse. The articles in this two-part Special Issue encapsulate the immense progress being made in the characterization and treatment of co-occurring disorders stemming from trauma and substance misuse yet also highlight the numerous remaining issues facing researchers and clinicians.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

DJOR is funded by K01AA026005.