Little is known about the health outcomes of clinician-supervised, performance-based, abstinence-contingent therapeutic work programs on homeless persons with addiction disorders. This study examined the effect of the Department of Veterans Affairs compensated work therapy program (CWT) on nonvocational outcomes. With mandatory urine screenings and adherence to addiction treatment schedules, CWT provided work opportunities (wages, hours, and responsibilities) with jobs created from Veterans Affairs contracts competitively obtained from private industry.
Homeless, substance-dependent veterans (N = 142) from 4 Department of Veterans Affairs medical centers were randomized, assessed at baseline, and reassessed at 3-month intervals for 1 year. Both CWT and control groups had access to comprehensive rehabilitation, addictions, psychiatric, and medical services. Data were analyzed to determine an immediate CWT effect after treatment and rates of change during 1 year.
Compared with control subjects, patients in the CWT program were more likely to (1) initiate outpatient addictions treatment, (2) experience fewer drug and alcohol problems, (3) report fewer physical symptoms related to substance use, (4) avoid further loss of physical functioning, and (5) have fewer episodes of homelessness and incarceration. No effect on psychiatric outcomes was found.
Work therapy can enhance nonvocational outcomes of addiction treatment for homeless persons, although long-term gains remain unknown.
MENTAL HEALTH professionals often refer clients to clinical programs where the primary goal is competitive employment. These programs of vocational rehabilitation, sheltered workshops, job clubs, and transitional and supported employment have shown varying degrees of success in helping the mentally ill attain employment.1-5 However, the relationship between structured work and nonvocational health outcomes remains inconclusive.
In contrast, economists consider productive work as an outcome of a healthy labor force.6 Epidemiologists emphasize work-related illnesses,7 hazards,8,9 stresses,10,11 and adverse health behaviors.12 Public health research finds retirement often leading to poorer physical functioning,13-15 somatic complaints,16 and fatal heart attacks,17 although it is unclear whether retirement resulted in or from poor health. What is not known is whether structured work can change health behaviors and, thus, health status.
The current study focuses on the Department of Veterans Affairs (VA) compensated work therapy (CWT) program, a clinician-supervised, abstinence-contingent, performance-based work program for homeless persons. The CWT program offers pay rewards but requires random drug testing and adherence to a schedule of outpatient addiction services determined to be clinically appropriate for each client. The program's clinical setting ensures that the link between work performance (productivity and presentation) and health behaviors (sobriety and use of addiction services) to job rewards (wages, hours, and responsibilities) are not undermined by the vicissitudes of labor markets. The study focused on homeless persons who lack regular employment and structured environments. Study outcomes included substance dependence behaviors (substance consumption and use of addictions treatment services), health outcomes (addiction-related physical symptoms, psychiatric symptoms, and health functioning), and other aspects of quality of life (rates of incarceration and homelessness). The study was set at VA medical centers where all clients had access to comprehensive health services, including addictions treatment and vocational rehabilitation. Access to care did not depend on employment status.
Subjects were recruited from homeless centers and addiction units at 4 VA medical centers located in Bedford, Mass; Northampton, Mass; Topeka, Kan; and St Cloud, Minn. Qualifying subjects (1) were eligible for VA care,(2) were homeless at intake, (3) satisfied DSM-III-R criteria for substance dependence or abuse,18 and (4) were willing to enter a therapeutic work program. For this study, homeless persons have "a primary nighttime residence that is a supervised publicly or privately operated shelter designed to provide temporary living accommodations, an institution that provides a temporary residence for individuals intended to be institutionalized, or a public or private place not designed for, or ordinarily used as, a regular sleeping accommodation for human beings"(McKinney Act, 42 USC 11302). Excluded patients were those (1) institutionalized at intake, (2) mentally or physically unable to work in the opinion of the CWT admitting clinician, (3) diagnosed with a terminal illness, (4) planning to leave the study service area within 1 year, or (5) unresponsive at the intake interview.
First introduced in 1957 (38 USC 1718), the VA CWT programs19 teach work discipline with abstinent-contingent, performance-based work for pay in staff-supervised, structured settings. As administered at the 4 study sites between July 1, 1994, and March 31, 1997, CWT offered work opportunities (continued employment, higher wages, hours, promotion, and responsibility) based on client work performance (productivity, reliability, presentation, and punctuality) and health behavior (sobriety and use of recommended addiction services) as judged by CWT clinicians through client observation, random drug screenings, and chart reviews. The CWT combined elements of supported employment(nontrivial wages paid from revenues earned from private sector contracts) and stepwise programs (clinician supervision and VA workshops). Consequences for inappropriate behaviors (positive drug screenings) varied from a reprimand to program dismissal and loss of CWT employment. Unfettered by informal organizations, appellate bureaucracies, and labor regulations, clinician managers were free to protect the integrity of work incentives and make judgments in the client's best interest. Control patients were not enrolled in CWT for at least the 1-year follow-up, although both subjects who received CWT and control subjects had full access to VA comprehensive medical, mental, addictions, and vocational rehabilitation services, including job-seeking skills and support, job documentation and interviewing techniques, and career counseling and assessment.
We hypothesized that the mandatory addiction treatment and drug screening protocols in CWT, among other factors, would have an immediate impact on addiction status as assessed by patient use of drugs and alcohol, and secondarily on patient use of addiction services and prevalence of substance use–related symptoms. We also hypothesized that subjects in the CWT group would gradually experience better psychiatric and medical status during the 1-year follow-up after CWT began.
Research assistants at each of the 4 study sites admitted patients, checked eligibility, administered baseline questionnaires, and then called a national coordinator (A.W.) in Dallas, Tex, to receive a patient identification number. Once the subject was assigned to a number, the coordinator revealed treatment assignment by opening, in sequence, sealed envelopes that had been addressed to both site and patient identification number. The enclosed assignments were based on random numbers generated by an SPSS program (SPSS Inc, Chicago, Ill). To attract subjects, a sampling ratio of 1 (control) to 4 (subject in CWT) was adopted. Subjects randomized to CWT were offered employment as soon as a CWT-sponsored job became available, usually within 6 days. After the baseline interview, neither patient nor assessors were blinded to study assignments.
Data came from face-to-face interviews conducted at baseline and at 3-month intervals for 1 year by trained interviewers under supervision of master's- or doctorate-level prepared social workers and psychologists. Information was verified by VA computerized file extracts and patient chart reviews. To ensure reliability of data collection, interviewers received group training, participated in routine conference calls, and were tested by rating prerecorded taped interviews.
As the primary measure, addiction status was determined by the Addiction Severity Index (ASI),20-22 summarizing drug and alcohol use problems into composite scores ranging from 0 to 1, with higher scores indicating more problems. Administered under confidential circumstances, these measures have been shown to be valid.23 As confirmatory measures of outcome, addiction care–seeking behavior was represented by a dichotomous variable that assumed a value of 1 if the patient had obtained at least 1 outpatient addiction visit during a 3-month period before each follow-up interview, and 0 otherwise. Substance use–related physi cal problems were measured as a simple count of 11 symptoms that included the presence or absence of seizures, delirium tremens, or memory trouble; seeing or hearing things not there after cutting down on substance use; liver disease; hepatitis or yellow jaundice; vomited blood or other stomach troubles; tingling or numbness in feet; inflammation of pancreas or pancreatitis; drug overdose; subacute bacterial endocarditis; cellulitis or other infections due to intravenous drug use; and continued use when aware that consumption may exacerbate serious physical illness.
Exploratory outcomes included psychiatric status assessed by a normalized global Brief Symptom Inventory,24,25 the ASI Psychiatric Status, and the Mental and Social Functioning components of the 36-Item Short Form Health Survey from the Medical Outcomes Study (SF-36).26,27 Medical status was assessed with the Physical Functioning component of the SF-36 and the Medical Status component of the ASI. Other measures included presence or absence of episodes of criminal justice incarceration and homeless nights during the 3 months before each interview.
The cost of inpatient (outpatient) care was calculated in 3-month intervals by multiplying the number of days (visits) by a cost per day (per visit) and summed over all respective bed sections (clinic stops). Costs were calculated for medicine, psychiatry, and addiction and rehabilitation services. Unit costs were based on median cost (1997 US dollars) for VA medical centers. Data came from VA's cost files that include costs for professional time, supplies, indirect administrative support and building maintenance, and depreciation for equipment and buildings.28 Separate estimates were calculated for medical, psychiatric, and addiction and rehabilitation services.
Two-tailed χ2 (discrete) and t(continuous) tests compared group differences at baseline. Longitudinal outcome data were analyzed by hierarchical regressions with the use of HLM/3L software29 to compute outcome differences between CWT and control groups as a percentage of baseline scores (continuous measures) and an odds ratio (dichotomous measures).
Tracking homeless patients necessitated the use of parametric statistics to account for missing observations and variable intervals between follow-up interviews, discussed in clinical trials generally30 and mental health specifically.31,32 With these approaches, time of observation enters as an explanatory variable to determine whether measured outcomes change with time.33,34 Clinical programs are evaluated by detecting whether differences between treated and control subjects "grow" over time,35-37 although estimates are unbiased only to the extent that the occurrence of missing values and length of intervals between follow-ups are uncorrelated with treatment assignment. The approach permits one to adjust for patient use of other services as time-dependent covariates.
Traditional parametric approaches determine treatment effects by detecting whether differences in outcomes between treated and control patients grow with time. These growth strategies may not describe programs that focus on behavior (eg, addictions). Here, program benefits may mature immediately after treatment begins, only to diminish with time because (1) efficacy "wears off,"(2) efficacious alternatives help control clients "catch up," (3) the intervention only enhances the speed of recovery, or (4) the intervention postpones inevitable outcomes of an intractable disorder. Thus, we estimated immediate and growth-rate effects by means of a declining-effects model (T.M.K., Thomas J. Carmody, PhD, Trish Suppes, MD, PhD, A. John Rush, MD, M. Lynn Crismon, PharmD, Alexander L. Miller, MD, Marchia Toprac, PhD, and Madhukar Trivedi, MD, unpublished data, August 2001):
ysit = β0+ β1Isi+ β20Zt + β21ZtIsi + β30t + β31tIsi + β4csit + αs + usi + vsit,
where ysit is the outcome assessed for patient i at site s (s = 1, 2, . . . 4) at t quarters (3 months) past baseline (t = 0). To evaluate CWT, the "intent-to-treat" variable Isi assigns a value of 1 for patients randomized to CWT and 0 if assigned to the control group. Zt is a dummy variable that assumes a value of 1 for t>0, and 0 otherwise. The variable csit is use of care during 3 months before t, including psychiatric care (psychiatric status outcomes), medical care (medical outcomes), and addiction and rehabilitation services (addiction status). The use of care covariate was excluded when use of addiction services was the dependent variable. The usi and vsit are random variates representing each patient and each assessment, assumed to be independent and normally distributed with 0 mean and constant variance during the 1-year follow-up.
As with traditional models, the growth-rate effect (β31)describes how outcome differences between CWT and controls grow, or decline, with time. The immediate effect (β21) describes how a lump-sum difference in outcomes between CWT and control subjects may occur initially after active CWT. Thus, outcome difference between CWT and control subjects for t>0 equals β21 + β31t. Other parameters are the average starting value for control subjects (β0); difference between CWT and control groups at baseline (t = 0) (β1); initial "lump-sum" change in outcomes for control subjects (β20); growth rate in outcomes for control subjects (β30);use of care main effect (β4); and fixed effects reflecting site-specific differences in average outcomes (αs), with αs = 0 for s = 1, the reference site.
The equation simplifies to a growth model when β20 =0 and β21 = 0 and can be modified to a logistic regression for dichotomous outcome variables.
Data collection began July 19, 1994, with recruitment ending March 22, 1996, and follow-up assessments ending April 1, 1997. Figure 1 describes the progress through the trial of the original 1090 subjects who had been discharged from VA addiction programs and whose names were referred for study. The large number of no-shows and patients unable to be located reflects difficulties inherent in studying homeless populations. The final sample (N = 142) was evenly distributed among the 4 sites (37%, 22%, 21%, and 20%) and included 22 (15%) who completed 2 follow-ups; 21 (15%), 3 follow-ups; and 99 (70%), 4 follow-ups.
The final sample did not differ from the 201 excluded eligible subjects(181 nonconsenting and 20 lost to follow-up) with respect to demographic characteristics(mean age, 43.1 vs 41.9 years, t = 1.44, P<.15; African American, 26% vs 25%, t= 0.22, P<.83; years of education, 12.7 vs 12.6, t = 0.21, P<.84), cost of VA care during the year before baseline ($26 199 vs $25 133, t = 0.41, P<.68), and health status (ASI for alcohol problems, 0.36 vs 0.36, t= 0.03, P<.98; ASI for drug problems, 0.11 vs 0.12, t = 1.22, P<.23; physical symptoms relating to substance use, 3.52 vs 3.53, t = 0.04, P<.97; ASI psychiatric status, 0.39 vs 0.38, t = 0.25, P<.81; Brief Symptom Inventory global status, 0.002 vs 0.001, t = 0.16, P<.87; SF-36 Mental Functioning, 50.2 vs 50.6, t = 0.16, P<.87; SF-36 Social Functioning, 58.9 vs 57.8, t = 0.30, P<.77; ASI edical Status, 0.35 vs 0.29, t = 1.39, P<.17; and SF-36 Physical Functioning, 85.9 vs 84.2, t = 0.77, P<.44).
Despite a 12% loss to follow-up, Table 1 shows no statistically significant difference between the CWT(n = 111) and control (n = 31) groups for demographic characteristics and outcome measures assessed at baseline. During the year after baseline, both CWT and control groups had extensive use of health services, including psychiatric and rehabilitation care, although differences reached statistical significance only in inpatient medicine days and outpatient addiction visits.
Subjects assigned to CWT received a job within a median 6 days after baseline and worked a mean of 393 hours (SD, 474 hours) at an average wage of $4.04/h (SD, $1.80/h; range, $0.50/h to $10.75/h). Of hours worked, 58% were unskilled, 22% semiskilled, 16% skilled labor, and 4% clerical, sales, or technical related. Working subjects were screened for substance use an average 8.6 times (SD, 10.7), or approximately once every 20 work days. Among those tested, 44% had at least 1 positive screening, with 15% of screenings testing positive.
Utilization covariates (measured in dollars) were significant predictors of patient outcomes for ASI drug (β4 = 0.003, t393 = 2.25, P<.02) and alcohol(β4 = 0.008, t393 = 2.31, P<.02) use problems, psychiatric status (β4 = 0.011, t393 = 2.18, P<.03), number of substance use– related physical symptoms(β4 = 0.18, t393 = 3.85, P<.001), and SF-36 Mental Functioning (β4 = −1.07, t393 = 1.97, P<.049) and Social Functioning (β4 = −1.88, t393 = 2.53, P<.01).
The CWT immediate and growth-rate effects are presented in Table 2 for each of the 12 outcome measures as a percentage of average baseline scores (continuous) or as odds ratios(dichotomous). Consistent with expectations, CWT clients were initially 2.7 times more likely to use addiction treatment than their control counterparts. After adjustment for greater use of addiction treatment with ±SE, patients who received CWT experienced immediate reductions in drug (−44.7% ± 12.8%) and alcohol (−45.4% ± 9.4%) use problems, and the number of substance use–related physical symptoms (−64.4% ± 8.0%). These immediate differences tended to decline with time, although such a "catch-up" pattern was statistically significant for only the number of substance use–related physical symptoms. Here, group differences declined by 17.0% ± 5.1% per quarter as control subjects, unlike their CWT counterparts, experienced a reduction in symptoms during follow-up by an average of −19.2% ± 4.4% per quarter.
There were no significant difference in psychiatric status between the CWT and control groups on any of the 4 outcome measures. On the other hand, differences between CWT and control groups tended to grow during follow-up by −24.4% ± 8.7% per quarter on the basis of ASI Medical Status and 6.9% ± 2.0% per quarter on the basis of SF-36 Physical Functioning. However, these gains were due primarily to declining function among control subjects (ASI Medical Status, 23.9% ± 7.6% per quarter; SF-36 Physical Functioning, −6.2% ± 1.8% per quarter) rather than from improved functioning among subjects in the CWT group (ASI Medical Status, −0.4% ± 11.5% per quarter; SF-36 Physical Functioning, 0.6% ± 2.7% per quarter). Finally, patients in the CWT group were initially 30% and 10% as likely to report an episode of incarceration and homelessness, respectively, as their control counterparts.
In this randomized, controlled trial, we evaluated a clinician-supervised, performance-based work program that tied paid work opportunities (hours, wages, and responsibilities) to performance (productivity, punctuality, and reliability) and health behaviors (sobriety and use of addiction services). Among homeless, substance-dependent persons with expressed desires to work, CWT was associated with greater use of addiction services. Even after adjustment for use of health and rehabilitative services, these data suggest that CWT clients experienced fewer problems associated with substance use and fewer episodes of homelessness and incarceration. The CWT clients also did not report the same decline in medical status and physical functioning exhibited by control subjects. However, no work effect on psychiatric status was detected. These differences are remarkable given that both groups had extensive use of medical, psychiatric, addictions, and rehabilitation services from local VA medical centers. However, patients in the CWT group reported generally more inpatient days and outpatient visits, suggesting that these outcomes may come at the price of higher health care costs.
These findings are consistent with those of the Milby et al study40 of substance-abusing homeless persons, in which abstinent contingent work therapy was found to be associated with 36% fewer positive cocaine toxicologic tests within 2 months of beginning treatment. These results are also consistent with the findings of Bell et al41,42 that paid vs unpaid work at VA medical facilities was associated with symptom reductions for patients with schizophrenia or schizoaffective disorders, and with Rosenheck and Seibyl's43 observational study that showed that receiving care at a residential support facility offering therapeutic work, but requiring responsible behavior, was associated with substance abuse, but not psychiatric symptoms. These results contrast with findings from assertive community treatment programs for homeless substance abusers that failed to find high rates of abstinence,44 and from supported employment in competitive work environments that failed to find symptom reductions.33,45 However, these latter studies focused on severe mental illness.
It is unknown which CWT elements may have contributed to program outcomes: structured work, pay incentives for mandatory substance screenings and adherence to addiction treatment schedules, clinician supervision, and improved access to care. Comparing other studies, Ames and Janes46 found that boring, stressful, and isolating work can in fact contribute to substance use behaviors, while alcoholic subjects who returned to work were likely to remain sober, but only when the job discouraged drinking behaviors and offered structured supervision.47,48 A recent econometric analysis (2-stage least-squares adjusting for self-selection) of national survey data (1991 and 1993 National Health Interview Surveys) suggested that workplace bans were associated with a 5–percentage point reduction in smoking prevalence and a 10% reduction in daily consumption among smokers, and accounted for all of the explained variance in smoking reduction among workers relative to nonworkers.49 Additional study is needed to untangle how program elements contribute to outcomes. With the success of supported employment programs, however, future studies should consider how outcomes vary between clinical and competitive employment settings.
There are study limitations. Findings were limited to a VA setting, 142 subjects, 1 year of follow-up, a low consent rate (47%), and a 1:4 sampling ratio that further limited statistical power. Outcomes measures were based on patient self-reports, although between-group biases may be small. First, CWT drug screenings averaged once every 20 days, so that hiding information from independent research teams may have had little perceived consequence on work opportunities. Second, control subjects wanting to enter CWT after completing the study had incentives to also underreport symptoms. Third, reduced substance consumption was consistent with patterns observed for other outcomes, including use of addiction services, substance use–related symptoms, medical status, and other measures.
Biases associated with nonrandomly occurring missing data and variable intervals between repeated measures may also be small. Compared with control subjects, CWT clients had a comparable number of observations (3.6 vs 3.8; t = 1.44, P<.15) and time between observations (1.5 vs 1.4 quarters; t = 1.26, P<.21). Regression to the mean bias either works against study findings (symptom counts) or is small compared with estimated effect size (drug and alcohol use problems).
In summary, the VA's CWT program was associated with better addiction status and with fewer episodes of homelessness and incarceration, and appears to prevent further deterioration in medical status and physical functioning. More research is needed to assess long-term impacts and to determine the active program ingredients contributing to outcomes.
Submitted for publication December 3, 1999; final revision received December 14, 2001; accepted December 20, 2001.
This study was supported in part by the Department of Veterans Affairs, Health Services Research and Development Service grant IIR 92-043 and Research Career Scientist Award 92-403, Washington, DC, and by grant 5-R24-MH53799 from the National Institute of Mental Health, Bethesda, Md.
We thank Mary Kashner, Pauline Salyer, Perry Lambird, MD, Mona Sue Lambird, JD, George Moore, Robert D. Fowler, MD, Stephen Berman, MSW, and A. John Rush, MD, for their special contributions in advancing this study.
The opinions expressed herein are those of the authors and do not necessarily reflect the views of supporting agencies and sponsors.
Corresponding author and reprints: T. Michael Kashner, PhD, JD, Department of Psychiatry, The University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd, Dallas, TX 75390-9086.
J The ICCD benchmarks for clubhouses: a practical approach to quality improvement in psychiatric rehabilitation. Psychiatr Serv.
2001;52207- 213Google ScholarCrossref
SL Rehabilitation programs and outcomes. Ciardello
MDeds. Vocational Rehabilitation of Persons With Prolonged Psychiatric Disorders.
Baltimore, Md JohnsHopkins University Press1988;231- 263Google Scholar
DR An update on supported employment for people with severe mental illness. Psychiatr Serv.
1997;48335- 346Google Scholar
P Helping people with severe mental illness to obtain work: systematic review. BMJ.
2001;322204- 208Google ScholarCrossref
CR Implementing supported employment as an evidence-based practice. Psychiatr Serv.
2001;52313- 322Google ScholarCrossref
T Health, nutrition, and economic development. J Econ Literature.
1998;36766- 817Google Scholar
SM Sick building syndrome, work factors and occupational stress. Scand J Work Environ Health.
1996;22243- 250Google ScholarCrossref
B Report on work stress related to social structures and processes. Elliott
Ceds. Stress and Human Health
New York, NY Springer Publishing2001;119- 146Google Scholar
SV The influence of the work environment on cardiovascular health: a historical, conceptual, and methodological perspective. J Occup Health Psychol.
1996;142- 56Google ScholarCrossref
RW The association of job strain and health behaviours in men and women. Int J Epidemiol.
1997;26575- 583Google ScholarCrossref
E The effect of retirement on physical health. Am J Public Health.
1983;73779- 783Google ScholarCrossref
JF Is mandatory retirement overrated? evidence from the 1970s. J Hum Resources.
1983;18337- 358Google ScholarCrossref
C The effect of retirement on somatic complaints. J Psychosom Res.
1983;2761- 67Google ScholarCrossref
American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition. Washington, DC American Psychiatric Association1987;
Department of Veterans Affairs, Veterans Health Administration Handbook #1103.1. Washington, DC Department of Veterans Affairs March 1996;
CP An improved evaluation instrument for substance abuse patients: the Addiction Severity Index. J Nerv Ment Dis.
1980;16826- 33Google ScholarCrossref
KA Predicting response to alcohol and drug abuse treatment: role of psychiatry severity. Arch Gen Psychiatry.
1983;40620- 625Google ScholarCrossref
KA Increased effectiveness of substance abuse treatment: a prospective study of patient-treatment "matching." J Nerv Ment Dis.
1983;171597- 605Google ScholarCrossref
CP New data from the Addiction Severity Index: reliability and validity in three centers. J Nerv Ment Dis.
1985;173412- 423Google ScholarCrossref
PM Brief Symptom Inventory: Administration, Scoring, and Procedures Manual. Baltimore, Md Clinical Psychometric Research1982;
LR BSI: Brief Symptom Inventory: Administration, Scoring, and Procedures Manual. Minneapolis, Minn National Computer Systems Inc1993;
M The Medical Outcomes Study: an application of methods for monitoring the results of medical care. JAMA.
1989;262925- 930Google ScholarCrossref
B SF-36 Health Survey Manual and Interpretation Guide. Boston, Mass Health Institute, New England Medical Center1993;
TM Determining costs in VA: research design problems and solutions illustrated with case studies. Med Care.
1999;37suppl VAAS18- AS26Google Scholar
Jr HLM5: Hierarchical Linear and Nonlinear Modeling. Lincolnwood, Ill Scientific Software International Inc2000;
M Statistical methods for cost-effectiveness analyses. Control Clin Trials.
1996;17387- 404Google ScholarCrossref
LS Caring for Depression: A Rand Study. Cambridge, Mass Harvard University Press1996;
B Cost Outcome Methods for Mental Health. San Diego, Calif Academic Press1998;
E A randomized clinical trial of supported employment for inner-city patients with severe mental disorders. Arch Gen Psychiatry.
1999;56627- 633Google ScholarCrossref
JT Some conceptual and statistical issues in analysis of longitudinal psychiatric data: application to the NIMH Treatment of Depression Collaborative Research Program Dataset. Arch Gen Psychiatry.
1993;50739- 750Google ScholarCrossref
SW Hierarchical Linear Models. Newbury Park, Calif Sage Publications1992;
D Using growth modeling to examine systematic differences in growth: an example of change in the functioning of families at risk of maladaptive parenting, child abuse, or neglect. J Consult Clin Psychol.
1991;5938- 47Google ScholarCrossref
KL Mississippi Scale for Combat-Related Posttraumatic Stress Disorder: three studies in reliability and validity. J Consult Clin Psychol.
1988;5685- 90Google ScholarCrossref
P Patterns of positive readjustment in Vietnam combat veterans. J Trauma Stress.
1993;6179- 193Google ScholarCrossref
J Sufficient conditions for effective treatment of substance abusing homeless persons. Drug Alcohol Depend.
1996;4339- 47Google ScholarCrossref
RM Clinical benefits of paid work activity in schizophrenia. Schizophr Bull.
1996;2251- 67Google ScholarCrossref
PH Clinical benefits of paid work activity in schizophrenia: 1-year follow-up. Schizophr Bull.
1997;23317- 328Google ScholarCrossref
CL Effectiveness of treatment elements in a residential–work therapy program for veterans with severe substance abuse. Psychiatr Serv.
1997;48928- 935Google Scholar
C Impact of assertive community treatment on homeless persons with co-occurring severe psychiatric and substance use disorders. Community Ment Health J.
1997;33113- 122Google ScholarCrossref
RE The New Hampshire study of supported employment for people with severe mental illness. J Consult Clin Psychol.
1996;64391- 399Google ScholarCrossref
C A cultural approach to conceptualizing alcohol and the workplace. Alcohol Health Res World.
1992;16112- 119Google Scholar
DL Integrating career counseling and psychotherapy: a comprehensive treatment strategy. Psychotherapy.
1987;24794- 799Google ScholarCrossref
S The SHARP carwash: a community-oriented work program for substance abuse patients. Soc Work.
1990;3579- 80Google Scholar
E Do workplace smoking bans reduce smoking? Am Econ Rev.
1999;89728- 747Google ScholarCrossref