This longitudinal study expands our understanding of the relationships among anxiety/depressive symptoms, trauma exposure (lifetime and recent), PTSD, gender, and substance use following the index treatment episode among a severely impaired sample of individuals with co-occurring disorders.
Few background characteristics were associated with substance use over the follow-up. Specifically, a history of employment prior to treatment was associated with a lower risk of substance use. It is possible that an individual's ability to hold a job prior to treatment entry may serve as a proxy for better social and cognitive functioning and greater access to resources, which may facilitate their efforts to remain abstinent. In addition, women were more likely to use substances over the follow-up compared to men, after adjusting for other baseline characteristics such as frequency of substance use, number of substances used, number of prior treatment episodes, lifetime history of mental health treatment, type of psychiatric diagnosis, and anxiety/depressive symptoms. Interestingly, Latino participants were less likely to engage in substance use compared to Whites. In accord with previous studies (Rollins, O'Neill, Davis, & Devitt, 2005
), supervised housing over the follow-up was associated with a lower risk of substance use. Nearly all of the sample had prior episodes of mental health treatment, and most had prior substance abuse treatment; thus, the lack of variation in these treatment experiences may produce a “ceiling effect” which may account for the lack of association between prior treatment history and substance use over follow-up.
Consistent with expectations, higher levels of anxiety/depressive symptoms over the follow-up were associated with substance use after adjusting for background characteristics and prior treatment history. Further, congruent with findings reported by other investigators (i.e., Grella et al., 2008
; Walitzer & Dearing, 2006
), the association between anxiety/depressive symptoms and substance use over the follow-up did not differ by gender.
The study's design does not allow us to ascertain the causal direction of the relationship between anxiety/depressive symptoms and substance use. It is possible that individuals may have resumed substance use in an attempt to manage their anxiety/depressive symptoms, which would be consistent with both the self-medication hypothesis (SMH) and the reformulated addiction motivation model. At the same time, resumption of substance use may have generated higher levels of anxiety/depressive and psychiatric symptoms as suggested by the rebound effect hypothesis (REH) (Blume, Schmaling, & Marlatt, 2000
). A recent study of veterans with SUD-only and those with co-occurring disorders provides some support for these hypotheses (Tomlinson et al., 2006
). In accordance with the SMH, depressive and anxiety were the symptoms most commonly experienced prior to post-treatment substance use among both groups, however, contrary to the SMH, symptoms did not diminish following use. Rather, as predicted by the REH, individuals with co-occurring conditions reported an exacerbation of the symptoms associated with their psychiatric diagnosis (i.e., depression, anxiety, and psychotic symptoms) following use. Overall, the present findings, as well as the results of the earlier study of veterans, are consistent with the model proposed by Otto and colleagues (2004)
whereby individuals’ sensitivity to internally generated negative affect is part of a feedback loop involving chronic stress and substance use.
One implication of the present findings is that it may be beneficial to assess individuals’ anxiety sensitivity and their tendency to use avoidance as a form of managing anxiety/depressive symptoms. In addition, beliefs and expectations regarding the extent to which substance use can help ameliorate distress symptoms may contribute to the resumption of substance use. Importantly, the extent to which post-treatment use may contribute to behavioral and thought processes that increase anxiety/depressive symptoms should also be studied. Ideally, the use of ecological momentary assessment methodology (EMA) would allow better examination of the temporal sequencing of these symptoms and substance use (Shiffman & Stone, 1998
As documented by previous studies among treatment-seeking individuals with co-occurring disorders (Gearon et al., 2003
; Mueser et al., 1998
; Norman et al., 2007
; Resnick et al., 2003), trauma exposure was a common experience among participants of this study, with nearly all reporting lifetime
trauma and about one third reporting exposure over the 12-month follow-up period. At treatment entry, about one third of the participants also met criteria for PTSD (SUD + PSYC + PTSD). Consistent with recent findings (i.e., Norman et al., 2007
; Read, Brown, & Kahler, 2004
), a history of lifetime
trauma exposure and a PTSD diagnosis at treatment entry were not associated with an increased risk for substance use over the follow-up. In contrast, trauma exposure over the follow-up was associated with an increased risk of substance use after accounting for baseline frequency of substance use, a diagnosis of PTSD, length of participation in the index treatment episode, and other covariates. Also, contrary to expectation, females and individuals with higher levels of lifetime
trauma exposure, a history of interpersonal violence, and a PTSD diagnosis were not more vulnerable to the negative impact of recent
trauma. This suggests that individuals with co-occurring disorders are generally vulnerable to the impact of these experiences, regardless of gender or past trauma history.
The findings of this study agree with recent views suggesting that ongoing anxiety and depressive symptoms and the severity of trauma-related symptoms rather than the presence of a co-occurring PTSD diagnosis at treatment entry may contribute to substance use post-treatment (see Read et al., 2004
). In particular, the severity of trauma-related symptoms appears to be associated with an increased risk for substance use in situations involving negative emotional (i.e., depression, frustration, anger, and fear) and physiological states (Norman et al., 2007
). Individuals may find themselves attempting to sustain abstinence, while also managing their anxiety/depressive and trauma-related symptoms, and the symptoms associated with their psychiatric diagnosis.
Several limitations of this study should be mentioned. Reliance on retrospective self-reports of trauma exposure may lead to memory distortions and recall biases (Schraedley, Turner, & Gotlib, 2002
; Widom & Shepard, 1997
). Yet given the difficulties associated with obtaining independent verification of these events, and recent evidence suggesting adequate levels of test-retest reliability for measures of trauma exposure (Goodman et al., 2001
; Lauterbach & Vrana, 1996
), the study's reliance on self-reports does not represent a critical flaw. Also, this study did not assess all potentially traumatic events, however, the events assessed are widely considered to have the ability to elicit symptoms of clinical significance and contribute to the development of PTSD. In addition, the Structured Clinical Interview (SCID) for DSM-IV employed in this study is not the current “gold standard” for the diagnosis of PTSD (Weathers, Keane, & Davidson, 2001
). Nevertheless, the SCID has been widely used in clinical and research settings to identify psychiatric disorders and PTSD (Subcommittee on Posttraumatic Stress Disorder, 2006
). Importantly, the aims of the original study necessitated the assessment of other psychiatric disorders, as such, the use of the SCID allowed for the identification of PTSD and other disorders while minimizing the burden on participants.
The study's design does not disentangle the temporal sequencing between recent
trauma exposure, anxiety/depressive symptoms, and substance use. Although it is reasonable to assume that exposure to potentially traumatic events over the follow-up may contribute to higher levels of symptomatology, which in turn may contribute to a greater risk of substance use, other factors may account for this relationship. For example, the severity of anxiety/depressive symptoms reported is not solely the result of these experiences but may rather be explained by the exacerbation of trauma-related and psychiatric symptoms or some other individual characteristics such as coping (Ouimette et al., 1999
). Alternatively, it is unclear whether substance use over the follow-up may increase the risk of further trauma exposure, higher levels of anxiety/depression or psychiatric symptomatology. Specifically, substance use may have increased individuals’ vulnerability to further trauma exposure by contributing to lower social functioning and greater behavioral disorganization.
In addition, the differing time frames employed to assess trauma exposure (within the previous 6 months), anxiety/depressive symptoms (over the previous 7 days), and substance use (previous 30 days) over the follow-up further challenge our ability to make causal inferences. Alternatively, assessing anxiety/depressive symptoms and substance use over long-time periods may increase the risk of reporting biases, which may be especially problematic in this severely impaired population. Furthermore, objective verification of self-reported substance use via urinalysis requires assessing use over a narrow time frame (i.e., few days to a week) which makes testing over a period of several months less feasible. Regarding trauma exposure, assessing exposure over a narrower time period (i.e., past 7 or 30 days) would have decreased the study's ability to capture events that may occur somewhat infrequently and would provide no information about events experienced prior to that narrow interval. Future studies might consider the use of EMA to determine the temporal ordering of these variables or, alternatively, researchers may consider conducting more frequent follow-ups to assess these variables within the same time frame. However, it is unclear whether the use of EMA or more frequent assessments would be feasible given the unique characteristics of this population and the increased burden these strategies would place on participants.
Finally, because this sample includes only participants from the treatment program who met the study's inclusion criteria (i.e., presence of co-occurring disorders) and data from those who were not eligible for participation were not collected, it is unclear to what extent this sample is representative of the population served by these programs. Despite these limitations this is one of the very few longitudinal studies examining the impact of anxiety/depressive symptoms, lifetime and recent trauma exposure (post-treatment), and PTSD, on substance use over time among individuals with co-occurring disorders. A unique strength of the study was the diversity of the sample which allowed the examination of potential gender differences.
The high rates of trauma exposure and re-exposure among this population suggest that researchers and treatment providers may benefit from routinely assessing trauma exposure both during and post-treatment. Also, as suggested by recent findings related to treatment and prevention of substance use relapse among individuals with trauma histories and PTSD (Morrissey, Jackson, Ellis, Amaro, Brown, & Najavits, 2005
) and those with co-occurring disorders (i.e., Drake, Wallach, & McGovern, 2005
), providers would benefit from incorporating relapse prevention interventions not only during the initial treatment episode but as part of ongoing care for this population. Relapse prevention efforts should include skills training aimed at helping individuals identify internal and external cues for use, acknowledge and manage negative emotions, and at learning skills to more effectively manage their anxiety/depressive and psychiatric symptoms (Otto et al., 2004
). In addition, these services need to incorporate training aimed at teaching individuals how to identify, anticipate, and avoid situations that may lead to further trauma exposure and increase the likelihood of substance use.
The literature on the development and implementation of trauma-informed services for women can guide efforts aimed at addressing the needs of this population. Services for individuals with co-occurring disorders and trauma histories need to be “integrated,” that is, they need to address all mental health, substance abuse, and trauma concurrently (Markoff, Reed, Fallot, Elliott, & Bjelajac, 2005
). Recent studies on treatment outcomes among women with co-occurring disorders and trauma histories have demonstrated that the provision of “integrated” counseling services was associated with greater improvements in the severity of alcohol and drug use, and psychological distress following treatment relative to usual care (Cocozza et al., 2005
; Morrissey et al., 2005
). Moreover, as suggested by other investigators, efforts at promoting long-term abstinence and recovery in this population need to include services aimed at addressing poverty, unemployment, promoting safe and supervised living situations, and the development of supportive social relationships (Drake et al., 2005
; Markoff et al., 2005
Several empirically validated treatment models for addressing the needs of individuals with co-occurring disorders have been developed (Markoff et al., 2005
). Of these treatments, “Seeking Safety” has the most empirical support (Najavits, 2007
). This treatment program aims to provide individuals with cognitive, behavioral, and interpersonal skills that will allow them to safely cope with the symptoms associated with SUDs and PTSD (Najavits, 2003
). This model has demonstrated utility in reducing psychiatric and trauma-related symptoms among women (Hien, Cohen, Miele, Litt, & Capstick, 2004
), men (Najavits, Schmitz, Gotthard, & Weiss, 2005
), homeless female veterans with co-occurring disorders (Desai, Harpaz-Rotem, Najavits, & Rosenheck, 2008
), women with substance use disorders who had been exposed to complex trauma (Cohen & Hien, 2006
), and incarcerated women (Zlotnick, Najavits, Rohsenow, & Johnson, 2003
The prevailing emphasis on continuing care approaches for substance use (McLellan 2002
; McLellan, Lewis, O'Brian, & Kleber, 2000
) focus on the chronic nature of these disorders which necessitate the maintenance of long-term behavioral changes. The continuing goal to implement these approaches for individuals with co-occurring disorders who demonstrate poorer long-term outcomes and more enduring trajectories of substance use than individuals with substance use disorders only (Chi et al., 2007) remains a challenge.