in today 's cost - conscious health care environment , equity and efficiency are becoming increasingly important considerations in managing and evaluating health care systems , especially as pressure to contain further growth in health care expenditures increases . equity and efficiency are an integral and essential part of a well functioning health care system . equitable and efficient health care systems will identify those in need of care , allow timely access to appropriate providers for adequate level of care , and protect service users against the risk of high expenditures . an efficient health care system will also induce proper and cost - effective provider and consumer behaviors through appropriate payment and benefit design . among many sectors of health care , the mh / sa care system has been particularly challenged with problems in equity and efficiency . studies have documented that access in mh / sa remains a serious problem . not only is mh / sa care manpower concentrated in certain areas , but also the geographic distribution of mh / sa care facilities is very uneven in the united states . in terms of service use , many studies raise concerns over an inefficient and inequitable pattern ; underutilization of services among the severely ill and vulnerable population and potential overutilization of care among the less serious may indicate problems in the system ( frank and lave , 1986 , lave and frank , 1988 ) . faced with many challenges , players in the mh / sa care system have searched , and continue to search , for ways to enhance the system 's equity and efficiency . significant legislative progress toward a more equitable provision of mh / sa care recently took place at the federal level through the mental health parity act of 1996 ( public law 104 - 204 ) . taking effect on january 1998 , the act requires that mental benefit provisions be no more restrictive than medical / surgical benefits in group health plans with 50 or more employees . at the state level , 13 states had already enacted a statewide mental illness parity laws , while three additional states enacted a parity law applicable only to state employees ( american managed behavioral healthcare association , 1997a ) . another notable activity in the current mh / sa market is the proliferation of new delivery and payment models , i.e. , managed behavioral health care . nearly absent a couple of decades ago , the managed behavioral health industry is estimated to cover approximately 170 million americans for their mh / sa care in 1997 ( american managed behavioral healthcare association , 1997b ) . and growth is expected to continue as more state medicaid programs adopt a managed behavioral care model . in such a dynamic and evolving market , we need to appraise the impact of new developments on access , use , and financing of mh / sa care . concomitant with the health care financing review 's interest in mh / sa care research , this issue disseminates research findings on access , use , and financing of mh / sa care for vulnerable populations . from 1980 - 85 , a comprehensive mh / sa epidemiological survey was conducted by the national institute of mental health ( nimh ) . known as the epidemiological catchment area ( eca ) study , the survey revealed a surprisingly high prevalence of mh / sa disorders in america . in a given month , about one in six adults are found to have a mh / sa disorder , and approximately one in four adult americans meet the criteria for mh / sa disorder during a year . equally surprising was that , of the population with mh / sa disorders , only one - half of them received mh / sa care at all , and less than one in three receive care within 1 year ( reiger et al . , 1993 ) . mental disorders encompass a broad range of conditions with different degrees of debilitating effects . as such , prevalence alone does not adequately depict the problems in mh / sa care need in america . based on the eca study conducted between 1980 and 1985 , the nimh estimates some five million adults are suffering from often incapacitating severe mental disorders , such as schizophrenia , manic - depressive illness , major depression , panic disorder , and obsessive - compulsive disorder . it was reported that about 60 percent of the persons with severe mh / sa disorders received care ( goodwin et al . , 1993 ) . a recent nationally representative survey , the national comorbidity survey reconfirmed this figure ( kesseler et al . prevalence of severe mh / sa disorders among children are not as well understood . however , according to a recent survey , mental disorders in child and adolescent populations ( meca ) , 3.2 percent of the sample adolescent population had a severe mh / sa disorder ( national institute for mental health , 1993 ) . accurate assessment of the need for hm / sa care is an essential guide in formulating a policy that allocates resources efficiently and equitably . especially in today 's changing health care market , we have to know what the current need is and to what extent these vulnerable population receive care . changing population characteristics and family and social structures necessitate continuous tracking of trends in need for mental health care . in an effort to assess the need and treatment in substance abuse care , this issue features an article by woodward and colleagues . this article presents new estimates of the numbers of persons in this country who need and receive substance abuse treatment . additionally , a summary of mental health data from the medicare current beneficiary survey ( mcbs ) round 13 is featured . as previously discussed , the epidemiological evidence clearly indicates we have serious problems with unmet needs among vulnerable populations . more than any other factors , the unequal provisions of mental health benefits in health insurance seems to have perpetuated this problem . rightfully fearing that generous mh / sa benefit would draw unfavorable selection , many private health insurance plans limited their mh / sa care benefits over time ( schuttinga , falik , and steinwald , 1985 ) . if the mental health parity act can restore equity in the provision of mh / sa benefits , it would considerably alleviate the inequity problem . with the rising concern over the health care expenditure inflation , we need to be more resourceful in planning and allocating resources . ( 1990 ) estimated the total expenditure for mh / sa in this country to be as much as $ 67 billion in 1990 . this amounts to approximately one - tenth of the total national expenditure on health care for the same year . studies indicate evidence of an inefficient pattern of service utilization in mh / sa care : underutilization of services among the severely ill and potential overutilization of care among the less serious . to enhance equity and efficiency in the system , it is important to monitor patterns of service utilization . in this issue of the review , there are a number of articles related to mh / sa service utilization in medicare and medicaid . rosenbach and ammering analyze medicare 's impact of mental health outpatient coverage expansion on utilization and expenditure between 1987 and 1992 . ettner and hermann examine the pattern of mental health specialist use in medicare , and report the factors that influence specialist use . an article by slifkin and colleagues proposes a reimbursement system for the care of the mentally retarded in intermediate care facilities . an article by cano , hennessy , warren , and lubitz presents information on demographic , diagnostic , utilization , and expenditure characteristics associated with inpatient psychiatric care among medicare beneficiaries in 1995 . the most sweeping change in the recent mh / sa system is the proliferation of managed mental health care . survey data show that the industry nearly doubled in covered lives between 1993 and 1997 ; the latest estimate puts the enrollment figure at approximately 170 million in 1997 ( american association for marriage and family therapy , 1996,american managed behavioral healthcare association , 1997b ) . this means approximately two - thirds ( 68 percent ) of the insured population are enrolled in a managed mh / sa care plan . this industry 's phenomenal expansion was driven , in part , by implementation of medicaid waivers in many states , a trend which seems certain to persist for the next several years . a total of 28 states and the district of columbia have implemented some form of managed mh / sa care waiver . nine states already received approval on their waiver requests , and ten additional states have pending waiver requests with various managed mh / sa care provisions . the managed mh / sa care contracts typically feature such characteristics as carved - out mh / sa benefits , person - level capitated budgets , risk sharing arrangements , and case management . compared with the incentives in indemnity insurance , each feature of the managed care contract can differently impact the utilization , financing , and outcome of the mh / sa care . at a time when the managed behavioral health system is emerging as the dominant mh / sa care delivery model , timely evaluation of its performance the third group of articles in this issue address this issue both empirically and theoretically . an article by stoner and colleagues evaluates a capitation payment demonstration in the community mental health centers ( cmhcs ) in the utah medicaid program . the authors report how capitation affected utilization and expenditures in three cmhcs . using afdc carve - out experience from massachusetts , norton , lindrooth , and dickey investigate whether the managed mh / sa care vendor shifted costs to the medical care sector . the findings from this relatively mature managed public program will be of great interest to other states that are at an early stage of managed behavioral care contracting . based on economic theory , frank and colleagues address the problem of adverse selection in the context of behavioral health care , and offers an explanation of why carve - out and cost sharing  two key features of managed behavioral contracts offer a solution to this problem . the mh / sa care system in america is undergoing a sweeping transformation . while shifting demographics and social and family structure affect the need for mh / sa care , new financing and delivery models are emerging in both the private and public sector . in this highly dynamic and often uncertain era the articles presented in this issue of the review describe , analyze , and evaluate the transformations that are taking place in the mh / sa care system . it is our hope that such research activities ultimately help shape a more equitable and efficient mh / sa care system .
this overview presents an introduction to the articles published in this issue of the health care financing review , entitled  mental health services and vulnerable populations . 
 this article discusses the challenges the mental health and substance abuse ( mh / sa ) care system is confronted with in terms of equity and efficiency and how the system is responding to these challenges . 
 it further addresses research issues in assessing the need and use of mental health services and summarizes recent activities in the research and evaluation of new delivery and payment systems .