The findings of the present study revealed that the prevalence of diagnoses of several types of prescription drug abuse and dependence increased significantly from 1991–1992 to 2001–2002. In particular, diagnoses of sedative abuse, sedative dependence, opioid abuse, and opioid dependence increased between these two time periods. These upward trends mirror and extend similar increases observed in prescription drug use disorders and non-medical use of prescription drugs over this same time period in the United States (Johnston et al., 2007
; McCabe et al., 2007a
; Blanco et al., 2007
). While the increases in past-year diagnoses of prescription drug abuse and dependence between 1991–1992 and 2001–2002 represent a concern, the actual prevalence rates of prescription drug abuse and dependence remain lower than the prevalence of alcohol and marijuana use disorders in the United States (Stinson et al., 2005
; Compton et al., 2004
; Grant et al., 2004
). Nevertheless, the results of the present study provide an improved understanding of the patterns associated with prescription drug use disorders and have several important implications for substance abuse treatment efforts.
If the increases from the present study were extrapolated to the total U.S. adult general population, the number of U.S. adults who met the criteria for past-year prescription drug abuse increased from approximately 314,891 in 1991–1992 to 579,009 in 2001–2002 and the number of U.S. adults who met the criteria for past-year prescription drug dependence rose from approximately 232,007 to 425,601 over this same time period. Furthermore, the majority of individuals with past-year diagnoses of prescription drug abuse and dependence also met criteria for another past-year substance use disorder in both 1991–1992 and 2001–2002. For instance, more than 60% of individuals with a past-year prescription opioid disorder met the criteria for another past-year substance use disorder. Our results extend the findings of previous studies that show individuals with alcohol use disorders have increased odds of prescription drug use disorders and nonmedical use of prescription drugs compared to individuals without alcohol use disorders (McCabe et al., 2006
; Stinson et al., 2005
; Johansson et al., 2003
The increase in prescription drug use disorders and co-occurrence with other substance use disorders could partially contribute to a shift in primary drugs of abuse observed in substance abuse treatment programs in the United States between 1993 and 2003 (SAMHSA, 2006c
). Indeed, there is evidence that the substance abuse profile of individuals entering substance abuse treatment in the United States changed in the past decade according to the Treatment Episode Data Set (TEDS), which collects data on admissions to substance abuse treatment facilities (SAMHSA, 2006d
). For instance, the percentage of substance abuse treatment admissions reporting alcohol as the primary substance of abuse decreased from 57% in 1993 to 41% in 2003, while the percentage of substance abuse treatment admissions for marijuana, opiates and stimulants increased from approximately 22% in 1993 to 41% in 2003 (SAMHSA, 2006c
Recent research has indicated that the majority of people with prescription drug use disorders did not receive substance abuse treatment (Blanco et al., 2007
; Huang et al., 2006
). The present study extended previous work and examined substance abuse treatment utilization separately for those individuals with a past-year diagnoses of prescription drug abuse and dependence. This more detailed approach revealed that approximately 86% of those with past-year prescription drug abuse and about 46% of those with past-year prescription drug dependence had not received substance abuse treatment in the previous 12 months in 2001–2002. Consistent with research on individuals with alcohol use disorders, the most prevalent form of substance abuse treatment reported by those with prescription drug abuse and dependence was 12-step meetings such as Alcoholics Anonymous and Narcotics Anonymous (Cohen, 2007
Based on these results, more efforts are needed to identify individuals with prescription drug abuse and dependence and remove potential barriers for substance abuse treatment utilization. The present study found the two leading reasons among individuals who believed they should ever utilize treatment but did not go, were the belief that one should be strong enough to handle a drug problem alone and the expectation that the drug problem would improve spontaneously. Health professionals in primary care settings can use this information to educate and motivate individuals to utilize substance abuse treatment. At least one study found that primary care physicians believed discussions with patients regarding prescription drug abuse were more difficult than discussions regarding alcohol abuse or depression (NCASA, 2000
). Clinicians are encouraged to conduct thorough drug use histories when working with individuals they suspect meet criteria for prescription drug abuse and dependence. In particular, screening efforts for prescription drug use disorders should assess polydrug use and the presence of co-occurring psychiatric disorders. Health professionals (e.g., private physicians, psychiatrists, psychologists, and social workers), drug detoxification facilities and substance abuse treatment programs should monitor for withdrawal from multiple substances when working with patients detoxifying from prescription drugs since these are the three most prevalent types of substance abuse treatment utilized by those with prescription drug dependence.
There are several strengths and limitations that are noteworthy based on the objectives of the present study. The NLAES and NESARC used similar methodology and contained nearly identical survey wording which allowed for valid comparisons of estimates based on data collected in these two national studies. For instance, the inclusion of DSM-IV criteria to assess substance use disorders in 1991–1992 and 2001–2002 represents an important strength for these two national studies. The large, nationally representative samples of the NLAES and NESARC allowed for calculation of national prevalence estimates for several individual prescription drug classes and types of substance abuse treatment.
There were also some limitations that should be taken into account while considering implications of the findings. First, the prevalence estimates of prescription drug abuse and dependence were underestimated because participants who used a drug less than 12 times in their lifetime were not considered in order to make the 2001–2002 NESARC estimates directly comparable to the 1991–1992 NLAES estimates. The omission of such individuals resulted in lower estimates of prescription drug use disorders, and the adjustment had a greater impact on prevalence estimates of abuse than dependence. For example, the prevalence of past-year nonmedical prescription opioid abuse in the NESARC was 0.24% without restricting to those who used prescription opioids 12 or more times in their lifetime as compared to 0.17% when restricting to those who used prescription opioids 12 or more times in their lifetime (). In contrast, the prevalence of past-year nonmedical prescription opioid dependence in the NESARC was 0.11% without restricting to those who used prescription opioids 12 or more times in their lifetime as compared to 0.10% when restricting to those who used prescription opioids 12 or more times in their lifetime. Second, since the present study represented secondary analyses, the survey items in the NLAES and NESARC limited what could be examined. The present study likely underestimated the prevalence of prescription drug use disorders some commonly misused prescription drugs (e.g. Vicodin, OxyContin, Ritalin, Adderall) were not listed that have been shown to have high rates of NMUPD (Johnston et al., 2007
; SAMHSA, 2006a
; Teter et al., 2006
). Furthermore, the measures to assess non-medical use of prescription drugs in the NLAES and NESARC failed to distinguish between patients who misused their own medication or alternatively, individuals who non-medically used someone else’s prescription drugs which subsequently led to prescription drug abuse and dependence. In addition, the treatment utilization questions were not asked separately for prescription drugs so the present study can not distinguish between treatment utilization for prescription drugs specifically or other drugs. Third, the NLAES and NESARC were interviewer-administered so caution should be exercised when comparing results from these studies and other sources of data.
Despite these limitations, the findings from the present study provide several important directions for future research. First, the prevalence and co-occurrence of prescription drug use disorders and other substance use disorders should continue to be monitored, due to the observed increases among certain subpopulations of individuals between 1991–1992 and 2001–2002 (such as males). Second, based on the high rates of co-occurrence, longitudinal data are needed to determine whether prescription drug use disorders develop before or after other substance use disorders. Finally, future research should examine the course, consequences and treatment associated with different subtypes of prescription drug use disorders.
In summary, the present study provides evidence that there was an increase in prescription drug abuse and dependence in the United States from 1991–1992 to 2001–2002. This increase coincides with a shift in substance abuse behaviors of individuals entering substance abuse treatment in the United States over this same time period. The results showed that the majority of individuals with prescription drug use disorders also met the DSM-IV criteria for an additional co-occurring substance use disorder. The findings also showed that only a minority of individuals with past-year prescription drug abuse and approximately half of those with past-year prescription drug dependence utilized some form of substance abuse treatment in the past 12 months. Taken together, these findings have important implications for treating prescription drug use disorders in the United States. In particular, substance abuse treatment efforts should be prepared to deal with increasing prevalence rates of prescription drug use disorders in the general population, high rates of co-occurring substance use disorders and underutilization of substance abuse treatment among those with prescription drug use disorders.