Effects of major depressive disorder and attention-deficit/hyperactivity disorder on the outcome of treatment for cocaine dependence

Potential effect of antidepressants on remission from cocaine use disorder - A nationwide matched retrospective cohort study

BACKGROUND

Cocaine use disorder (CUD) is a significant public health issue for which there is no Food and Drug Administration-approved pharmacotherapy. Depressive disorders are common psychiatric comorbidity amongst individuals with CUD.

METHODS

A retrospective cohort study was conducted among 161,544 patients diagnosed with CUD and depression to evaluate the effectiveness of 13 antidepressants on CUD remission. For any antidepressant found to be associated with CUD remission that had an additional indication, we conducted an additional analysis to evaluate the effectiveness of the candidate drug in patients with CUD with that indication. We then analyzed publicly genomic and functional databases to identify potential explanatory mechanisms of action of the candidate drug in the treatment of CUD.

RESULTS

Among these antidepressants, bupropion was associated with higher rates of CUD remission compared to propensity-score matched patients prescribed other antidepressants: hazard ratio (HR) and 95% confidence interval (CI) 1.57 (95% CI: 1.27-1.94). Bupropion is also approved for smoking cessation. We identified CUD patients with co-occurring nicotine dependence and observed that patients prescribed bupropion displayed a higher rate of CUD remission compared to matched individuals prescribed other drugs for nicotine dependence: 1.38 (95% CI: 1.11-1.71). Genetic and functional analyses revealed that bupropion interacts with four protein-encoding genes (COMT, DRD2, SLC6A3, and SLC6A4) which are also associated with CUD and targets CUD-associated pathways including serotonergic synapses, cocaine addiction, and dopaminergic synapses.

CONCLUSIONS

Our findings suggest that bupropion might be considered a treatment for improving CUD remission in patients with CUD and co-occurring depression or nicotine dependence.

Helpful or Harmful? The Therapeutic Potential of Medications with Varying Degrees of Abuse Liability in the Treatment of Substance Use Disorders

Purpose of Review

This review summarizes recent clinical trial research on pharmacological treatments for substance use disorders, with a specific focus on agents with potential abuse liability.

Recent Findings

Pharmacological treatments for substance use disorders may include gabapentinoids, baclofen, modafinil, ketamine, cannabinoids, gamma-hydroxybutyrate, and psychedelics. Gabapentinoids may decrease negative subjective effects of withdrawal in alcohol and cannabis use disorders. Cannabinoids similarly appear to decrease use and withdrawal symptoms in cannabis use disorder, while research shows stimulant medications may reduce cravings and increase abstinence in cocaine use disorder. Ketamine and psychedelics may help treat multiple substance use disorders. Ketamine may reduce withdrawal symptoms, promote abstinence, and diminish cravings in alcohol and cocaine use disorders and psychedelics may promote remission, decrease use, and reduce cravings in alcohol and opioid use disorders.

Summary

Regardless of current regulatory approval statuses and potentials for abuse, multiple agents should not be dismissed prematurely as possible treatments for substance use disorders. However, further clinical research is needed before effective implementation can begin in practice.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40429-022-00432-9.

A Retrospective Comparative Study in Patients With Cocaine Use Disorder Comorbid With Attention Deficit Hyperactivity Disorder Undergoing an rTMS Protocol Treatment

Background: Adult attention-deficit/hyperactivity disorder (ADHD) is associated with high comorbidity with other psychiatric diseases, including cocaine use disorder (CocUD). Given the common fronto-striatal dysfunction, ADHD patients often use cocaine as self-medication for ameliorating symptoms by increasing striatal dopamine release. Yet, comorbidity with ADHD is related to poor treatment outcomes. CocUD has been treated with transcranial magnetic stimulation (TMS), but no studies investigated the outcomes in patients comorbid with ADHD. Methods: Twenty-two ADHD/CocUD and 208 CocUD-only participants received a high-frequency (15 Hz) rTMS treatment stimulating the left-DLPFC. We investigated whether both groups of patients shared similar demographic and clinical characteristics at baseline. Then, we monitored the effect of treatment testing for potential differences between groups. Results: At baseline demographic, toxicology and clinical features were not different between the two groups except for global severity index (GSI from SCL-90): patients of ADHD/CocUD group reported higher general symptomatology compared to the CocUD-only group. Concerning the effect of treatment, both groups significantly improved over time regarding cocaine use, craving, and other negative affect symptoms. No differences were observed between groups. Conclusions: To our knowledge, this is the first study comparing the demographic characterization and rTMS clinical improvements of patients with a dual diagnosis of ADHD and CocUD against CocUD-only patients. Cocaine use and common self-reported withdrawal/abstinence symptoms appear to benefit from rTMS treatment with no differences between groups. Future studies are needed to further investigate these preliminary results.

A Clinician's Guide to Co-occurring ADHD among Adolescent Substance Users: Comorbidity, Neurodevelopmental Risk, and Evidence-based Treatment Options

This article introduces neurodevelopmental and clinical considerations for treating adolescents with co-occurring Attention-Deficit/Hyperactivity Disorder (ADHD) and substance use (ASU) in outpatient settings. We first describe neurobiological impairments common to ADHD and ASU, including comorbidity with conduct disorder, that evoke a profile of multiplicative developmental risk. We then present two evidence-based options for targeting ADHD-related problems during ASU treatment. Medication integration interventions utilize family ADHD psychoeducation to prompt decision-making about ADHD medication and integrate medication management into behavioral services. Clinic-based academic training interventions utilize family interventions to improve the home academic environment and boost organization skills. We conclude with recommendations for ADHD assessment and intervention sequencing.

Psychostimulant drugs for cocaine dependence

BACKGROUND

Cocaine dependence is a severe disorder for which no medication has been approved. Like opioids for heroin dependence, replacement therapy with psychostimulants could be an effective therapy for treatment.

OBJECTIVES

To assess the effects of psychostimulants for cocaine abuse and dependence. Specific outcomes include sustained cocaine abstinence and retention in treatment. We also studied the influence of type of drug and comorbid disorders on psychostimulant efficacy.

SEARCH METHODS

This is an update of the review previously published in 2010. For this updated review, we searched the Cochrane Drugs and Alcohol Group Trials Register, CENTRAL, MEDLINE, Embase and PsycINFO up to 15 February 2016. We handsearched references of obtained articles and consulted experts in the field.

SELECTION CRITERIA

We included randomised parallel group controlled clinical trials comparing the efficacy of a psychostimulant drug versus placebo.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 26 studies involving 2366 participants. The included studies assessed nine drugs: bupropion, dexamphetamine, lisdexamfetamine, methylphenidate, modafinil, mazindol, methamphetamine, mixed amphetamine salts and selegiline. We did not consider any study to be at low risk of bias for all domains included in the Cochrane 'Risk of bias' tool. Attrition bias was the most frequently suspected potential source of bias of the included studies. We found very low quality evidence that psychostimulants improved sustained cocaine abstinence (risk ratio (RR) 1.36, 95% confidence interval (CI) 1.05 to 1.77, P = 0.02), but they did not reduce cocaine use (standardised mean difference (SMD) 0.16, 95% CI -0.02 to 0.33) among participants who continued to use it. Furthermore, we found moderate quality evidence that psychostimulants did not improve retention in treatment (RR 1.00, 95% CI 0.93 to 1.06). The proportion of adverse event-induced dropouts and cardiovascular adverse event-induced dropouts was similar for psychostimulants and placebo (RD 0.00, 95% CI -0.01 to 0.01; RD 0.00, 95% CI -0.02 to 0.01, respectively). When we included the type of drug as a moderating variable, the proportion of patients achieving sustained cocaine abstinence was higher with bupropion and dexamphetamine than with placebo. Psychostimulants also appeared to increase the proportion of patients achieving sustained cocaine and heroin abstinence amongst methadone-maintained, dual heroin-cocaine addicts. Retention to treatment was low, though, so our results may be compromised by attrition bias. We found no evidence of publication bias.

AUTHORS' CONCLUSIONS

This review found mixed results. Psychostimulants improved cocaine abstinence compared to placebo in some analyses but did not improve treatment retention. Since treatment dropout was high, we cannot rule out the possibility that these results were influenced by attrition bias. Existing evidence does not clearly demonstrate the efficacy of any pharmacological treatment for cocaine dependence, but substitution treatment with psychostimulants appears promising and deserves further investigation.

Inoculation stress hypothesis of environmental enrichment

One hallmark of psychiatric conditions is the vast continuum of individual differences in susceptibility vs. resilience resulting from the interaction of genetic and environmental factors. The environmental enrichment paradigm is an animal model that is useful for studying a range of psychiatric conditions, including protective phenotypes in addiction and depression models. The major question is how environmental enrichment, a non-drug and non-surgical manipulation, can produce such robust individual differences in such a wide range of behaviors. This paper draws from a variety of published sources to outline a coherent hypothesis of inoculation stress as a factor producing the protective enrichment phenotypes. The basic tenet suggests that chronic mild stress from living in a complex environment and interacting non-aggressively with conspecifics can inoculate enriched rats against subsequent stressors and/or drugs of abuse. This paper reviews the enrichment phenotypes, mulls the fundamental nature of environmental enrichment vs. isolation, discusses the most appropriate control for environmental enrichment, and challenges the idea that cortisol/corticosterone equals stress. The intent of the inoculation stress hypothesis of environmental enrichment is to provide a scaffold with which to build testable hypotheses for the elucidation of the molecular mechanisms underlying these protective phenotypes and thus provide new therapeutic targets to treat psychiatric/neurological conditions.

Attention deficit hyperactivity disorder in cocaine-dependent adults: a psychiatric comorbidity analysis

BACKGROUND AND OBJECTIVES

Attention deficit hyperactivity disorder (ADHD) is highly prevalent among drug abusers. We studied the psychiatric comorbidity and characteristics of cocaine use in relation to the presence of ADHD among patients with cocaine dependence.

METHODS

A total of 200 cocaine-dependent patients attending an Outpatient Drug Clinic participated in the study. A systematic evaluation of ADHD (CAADID-II), the severity of addiction (EuropASI) and other axes I and II psychiatric disorders was made (SCID-I and SCID-II). A descriptive, bivariate, and multivariate analysis of the data was performed.

RESULTS

In the multivariate analysis, the identified risk factors for the development of ADHD were a history of behavioral disorder in childhood (OR: 3.04), a lifetime history of cannabis dependence in the course of life (OR: 2.68), and age at the start of treatment (OR: 1.08). The bivariate analysis showed ADHD to be associated with other factors such as male gender, age at start of cocaine use and dependence, the amount of cocaine consumed weekly, increased occupational alteration, alcohol consumption, general psychological discomfort, depressive disorder, and antisocial personality disorder.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

We conclude that ADHD is associated with increased psychiatric comorbidity and greater severity of addiction.

12-step affiliation and attendance following treatment for comorbid substance dependence and depression: a latent growth curve mediation model

Among substance-dependent individuals, comorbid major depressive disorder (MDD) is associated with greater severity and poorer treatment outcomes, but little research has examined mediators of posttreatment substance use outcomes within this population. Using latent growth curve models, the authors tested relationships between individual rates of change in 12-step involvement and substance use, utilizing posttreatment follow-up data from a trial of group Twelve-Step Facilitation (TSF) and integrated cognitive-behavioral therapy (ICBT) for veterans with substance dependence and MDD. Although TSF patients were higher on 12-step affiliation and meeting attendance at end-of-treatment as compared with ICBT, they also experienced significantly greater reductions in these variables during the year following treatment, ending at similar levels as ICBT. Veterans in TSF also had significantly greater increases in drinking frequency during follow-up, and this group difference was mediated by their greater reductions in 12-step affiliation and meeting attendance. Patients with comorbid depression appear to have difficulty sustaining high levels of 12-step involvement after the conclusion of formal 12-step interventions, which predicts poorer drinking outcomes over time. Modifications to TSF and other formal 12-step protocols or continued therapeutic contact may be necessary to sustain 12-step involvement and reduced drinking for patients with substance dependence and MDD.

Mediational relations between 12-Step attendance, depression and substance use in patients with comorbid substance dependence and major depression

AIMS

Among patients with substance dependence and comorbid major depressive disorder (MDD) receiving treatment in a controlled trial, we examined if group differences in depression were mediated by 12-Step involvement, and if the effects of 12-Step involvement on future alcohol and drug use were mediated by reductions in depression.

DESIGN

Controlled trial of Twelve-Step facilitation (TSF) and integrated cognitive-behavioral therapy (ICBT), delivered in out-patient groups for 6 months with adjunct pharmacotherapy.

SETTING

Out-patient dual diagnosis clinic in Veteran's Affairs Healthcare Center.

PARTICIPANTS

Veterans (n = 209) diagnosed with alcohol, stimulant or marijuana dependence and substance-independent MDD.

MEASUREMENTS

Twelve-Step attendance and affiliation, depression severity, percentage of days drinking and percentage of days using drugs assessed at baseline and months 3, 6 and 9.

FINDINGS

In multi-level analyses greater 12-Step meeting attendance predicted lower depression and mediated the superior depression outcomes of the TSF group, explaining 24.3% of the group difference in depression. Independent of treatment group, lower depression severity predicted lower future alcohol use and mediated the effects of 12-Step meetings, explaining 15.7% of their effects on future drinking. Controlled, lagged models indicated these effects were not confounded by current substance use, suggesting that depression had unique associations with 12-Step meeting attendance and future drinking.

CONCLUSIONS

For patients with substance dependence and major depressive disorder, attendance at 12-Step meetings is associated with mental health benefits that extend beyond substance use, and reduced depression could be a key mechanism whereby 12-Step meetings reduce future drinking in this population.

Psychiatric co-morbidity and substance use disorders: treatment in parallel systems or in one integrated system?

Psychiatric co-morbidity among substance users refers to the simultaneous presence of at least another psychiatric disorder in a person diagnosed with a substance use disorder. Co-morbid patients represent a substantial number of people in treatment and present greater disorder severity from both the clinical and social perspectives than those people diagnosed with only one type of disorder. We present an overview of the current state of the art concerning the choice of site of treatment, the kind of intervention, the length of such treatment, and future goals, aiming to establish a more effective intervention, and finally so as to further improve clinical outcomes.

Comorbid depression and substance use disorder: longitudinal associations between symptoms in a controlled trial

This study examined the longitudinal association between substance use and depressive symptoms in veterans receiving outpatient treatment for comorbid substance use disorder and major depression. Veterans (N = 237, mean age = 48.2 years, 90% male, 70% Caucasian) received either 6 months of group integrated cognitive-behavioral therapy or twelve-step facilitation. Hamilton Depression Rating Scale scores and percent days using any substance were assessed every 3 months up to 1 year posttreatment. Greater substance use predicted time-varying elevations in depression above individual patterns of change in depression. Moreover, change in depressive symptoms was associated with change in both the likelihood of any substance use and the frequency of use during the treatment and follow-up periods. Changes in these symptoms appear to be linked, such that individuals with greater reductions in substance use have greater reductions in depressive symptoms (and vice versa).

Antidepressants for cocaine dependence and problematic cocaine use

BACKGROUND

Cocaine dependence is a disorder for which no pharmacological treatment of proven efficacy exists, advances in the neurobiology could guide future medication development.

OBJECTIVES

To investigate the efficacy and acceptability of antidepressants alone or in combination with any psychosocial intervention for the treatment of cocaine dependence and problematic cocaine use.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, EMBASE and CINAHL in July 2011 and researchers for unpublished trials.

SELECTION CRITERIA

Randomised clinical trials comparing antidepressants alone or associated with psychosocial intervention with placebo, no treatment, other pharmacological or psychosocial interventions.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

37 studies were included in the review (3551 participants).Antidepressants versus placebo: results for dropouts did not show evidence of difference, 31 studies, 2819 participants, RR 1.03 (Cl 95% 0.93 to 1.14). Looking at Abstinence from cocaine use, even though not statistically significant, the difference shown by the analysis in the three-weeks abstinence rate was in favour of antidepressants (eight studies, 942 participants, RR 1.22 (Cl 95% 0.99 to 1.51)). Considering only studies involving tricyclics, five studies, 367 participants, or only desipramine, four studies, 254 participants, the evidence was in favour of antidepressants. However, selecting only studies with operationally defined diagnostic criteria, statistical significance favouring antidepressants, as well as the trend for significance shown by the full sample, disappeared. Looking at safety issues, the results did not show evidence of differences (number of patients withdrawn for medical reasons, thirteen studies, 1396 participants, RR 1.39 (Cl 95% 0.91 to 2.12)). Subgroup analysis considering length of the trial, associated opioid dependence or associated psychosocial interventions as confounding factors, failed in showing consistent and statistically significant differences in favour of antidepressants.Antidepressants versus other drugs: Comparing antidepressants with dopamine agonists or with anticonvulsants, no evidence of differences was shown on dropouts and on other outcomes (abstinence from cocaine use, adverse events).

AUTHORS' CONCLUSIONS

At the current stage of evidence data do not support the efficacy of antidepressants in the treatment of cocaine abuse/dependence. Partially positive results obtained on secondary outcome measures, such as depression severity, do not seem to be associated with an effect on direct indicators of cocaine abuse/dependence. Antidepressants cannot be considered a mainstay of treatment for unselected cocaine abusers/dependents.

Self-efficacy mediates the relationship between depression and length of abstinence after treatment among youth but not among adults

We present two studies testing whether self-efficacy mediates the relationship between depression symptoms and initial abstinence duration after substance use treatment in adolescents and adults. Study 1: Adolescents (N = 208) were recruited from substance use treatment in an urban/suburban area in the United States between 1999 and 2005 and were followed monthly after discharge. Measures used were affective state (depression symptoms), drug-taking coping self-efficacy, and length of abstinence after treatment. Self-efficacy fully mediated the relationship between depression and time to use. Study 2: In a similar study design, adult veterans (N = 160) in outpatient substance user treatment were interviewed during treatment and monthly following treatment. Depression was negatively associated with self-efficacy, and self-efficacy predicted time to first substance use, but there was no mediation. Study implications and limitations are noted.

Symptom prevalence of ADHD in a community residential substance abuse treatment program

OBJECTIVE

ADHD is a common comorbid condition with substance use disorder. This study seeks to examine the discrepancy in the prevalence rate between those previously diagnosed with ADHD and those diagnosed while in treatment. It is hypothesized that clients with ADHD would have earlier unsuccessful terminations from treatment than non-ADHD clients and that the ADHD Self-Report Scale (ASRS Version 1.1) would be a reliable predictor.

METHOD

Participants (N = 87) are admitted to a publicly funded 28-day residential treatment program. All participants are screened with the ASRS and participate in a clinical assessment evaluation.

RESULTS

A significant difference is found between the clinical record rate of 3.44% and the 43.68% rate found during treatment. The ASRS significantly predicts ADHD.

CONCLUSIONS

The use of the ASRS is recommended and should be incorporated into standard intake assessment protocols. Careful diagnostic interviews are urged to determine if clients in residential treatment have ADHD.

The relationship between depression and smoking cessation outcomes in treatment-seeking substance abusers

The National Drug Abuse Treatment Clinical Trials Network (CTN) recently completed a randomized, open label trial comparing treatment as usual (TAU) combined with nicotine patches plus cognitive behavioral group counseling for smoking cessation (n = 153) to TAU alone (n = 72) for patients enrolled in treatment programs for drug or alcohol dependence, who were interested in quitting smoking. This report is a secondary analysis evaluating the effect of depressive symptomatology (n = 70) or history of depression (n = 110) on smoking cessation outcomes. A significant association was seen between measures of depression and difficulty quitting cigarettes. Specifically, there was a greater probability for smoking abstinence for those with lower baseline Beck Depression Inventory II (BDI-II) scores. These data suggest that evaluation and treatment of depressive symptoms may play an important role in improving smoking cessation outcomes. (Am J Addict 2010;00:1-8).

Wie stark sind Erwachsene mit ADHS und komorbiden Störungen in ihrer gesundheitsbezogenen Lebensqualität beeinträchtigt?

Hintergrund: Zur ADHS bei Erwachsenen liegen nur wenige Studien vor, die den Zusammenhang zwischen einer ADHS und komorbiden Störung erheben und mit der gesundheitsbezogenen Lebensqualität in Verbindung bringen. Methode: Die Teilnehmer der Studie wurden per Kreuzklassifikation in Gruppen unterteilt, nachdem sie als auffällig oder unauffällig eingestuft wurden. Neben χ2-Tests und korrelativen Beziehungen wurden prädiktive Werte und das relative Risiko bestimmt, um den Zusammenhang zwischen ADHS, komorbiden Störungen und der gesundheitsbezogenen Lebensqualität zu ermitteln. Ergebnisse: Während bei wenigen und begrenzten ADHS-Symptomen kaum komorbide Störungen festzustellen waren, so treten in der Hälfte aller Fälle von ADHS weitere psychische Belastungsfaktoren auf. Dabei hatten ADHS-Betroffene ein deutlich höheres Risiko für das Vorliegen psychischer Beschwerden als die Nichtbetroffenen. Diskussion: ADHS ist mit erhöhter psychischer Belastung bei gleichzeitiger Abnahme der gesundheitsbezogenen Lebensqualität verbunden. Neben dem generellen Nachweis einer hohen psychischen Belastung bei ADHS hat dies wichtige Konsequenzen für Diagnostik und Therapie. So ist eine umfassende Differenzialdiagnostik nötig, damit eine Therapie auch komorbide Störungen einbeziehen kann und sich somit die gesundheitsbezogene Lebensqualität verbessern lässt.

Issues in the management of patients with complex attention-deficit hyperactivity disorder symptoms

Patients with attention-deficit hyperactivity disorder (ADHD) exhibit a wide range of symptoms related to functional impairment. Psychiatric comorbidities are highly prevalent among these patients, often emerging at an early age and persisting (or reoccurring) into adulthood. Among the most common types of comorbidities in children and adults are disruptive behaviour disorders such as oppositional defiant disorder and conduct disorder, mood disorders, anxiety disorders, and substance use disorders. The heterogeneous clinical presentation of ADHD, which also changes with maturation into adulthood, may often obscure the presence of psychiatric comorbidity. Co-occurring disorders frequently go undetected and lead to negative effects on psychosocial and long-term functional outcomes. As with uncomplicated ADHD, medication therapy combined with psychosocial interventions may be necessary. With comorbid disorders, two or more medications may be considered to appropriately manage both ADHD and the comorbid disorder. However, there are few studies that discuss combination medication treatments and there are no current US FDA-approved combined treatments for ADHD and comorbid conditions. This raises significant challenges and risks for poor tolerability and drug-drug interactions. Nevertheless, identification and appropriate treatment must be given a high priority for these highly vulnerable patients to derive optimal benefits from treatment.

Interventions for co-occurring addictive and other mental disorders (AMDs)

While research on the management of co-occurring addictive and mental disorders (AMDs) has grown substantially in recent years, we still have little guidance on specific strategies. Consideration of epidemiological research and ethical principles can supplement existing clinical trials in providing a way forward. High frequencies of co-occurring disorders, equity of access for affected individuals and potential clashes between services in priorities and procedures, suggest that a stepped model of care by a single service may often be required. Typically, problems are multiple rather than dual, with potential for mutual influence, suggesting a need for interventions that are sensitive to and encompass complex co-occurring problems. Motivational problems are endemic, initial gains are often partial and unstable, and relapses potentially have serious consequences, suggesting a need for long-term, assertive follow-up. Principles such as these provide a solid framework for designing both services and interventions. However, there is a continuing need for controlled trials that unpack effective components of interventions, and increase their impact.

Early abstinence in cocaine pharmacotherapy trials predicts successful treatment outcomes

There is a robust relationship between early and later abstinence in smoking cessation, but that relationship has not been explored among other substances of abuse. To assess whether early abstinence during treatment, as opposed to baseline abstinence, predicted later abstinence among cocaine-dependent patients, data from two randomized double-blind controlled clinical pharmacotherapy trials were analyzed. Similar to the findings in the smoking cessation literature, results indicate that abstinence in the first 2 weeks of pharmacotherapy predicted later in-trial abstinence. This finding has implications both for treatment research and for clinical practice, suggesting that patients who do not respond early in treatment may need a more intensive intervention.

Responding to the challenge of co-occurring disorders: suggestions for future research

This special issue consolidates some recent research findings and scientific thought on co-occurring disorders from both the substance abuse and mental health fields. This summary article recaps and synthesizes the main findings and themes, then considers additional issues in the field today to arrive at an agenda for future co-occurring disorders research. Plans must: (1) encourage and assist further development of treatment programs that respond to an array of types and severities of co-occurring disorders while taking into account the limited resources typically available; (2) continue the development and testing of continuing care models by exploring strategies that will sustain the recovery of treated individuals who remain vulnerable to relapse; and (3) contribute to our understanding of the mechanisms and processes that enable new interventions and practices to be adopted, implemented, and sustained. "Co-occurring disorders" is a relatively new area of research; this special issue illustrates the productivity of work to date and indicates the potential for advances to come.

The effects of cocaine: a shifting target over the course of addiction

Repeated exposure to psychostimulant drugs such as cocaine has been shown in numerous studies to produce significant neuroadaptations in both structure and function throughout the brain. Nonhuman primate models provide a way to systematically evaluate these adaptations engendered by cocaine self-administration and simulate the progressive nature of cocaine addiction in humans. Functional activity, measured using the 2-[14C]deoxyglucose method, was evaluated at selected critical time points over the course of chronic cocaine self-administration in rhesus monkeys. The effects of cocaine exposure in the initial stages of self-administration resulted in changes in functional activity in a highly restricted network of interconnected brain regions when compared to activity in food-reinforced controls. This pattern of changes was confined mainly to ventromedial prefrontal cortex and ventral striatum. Following chronic exposure to cocaine self-administration, however, the spatial extent and intensity of significant alterations in functional activity expanded considerably. The shift in topography of these changes was orderly, originating ventromedially in the prefrontal cortical-ventral striatal network and expanding dorsally to encompass the dorsal striatum. A strikingly similar progression occurred within the cortical areas that project to each of these striatal regions. Preliminary studies suggest that this pattern is maintained despite periods of abstinence from cocaine. The shifting patterns of cerebral metabolic function that accompany longer durations of cocaine self-administration may underlie many of the characteristics of chronic drug exposure, and may provide transitional mechanisms to more compulsive cocaine use.