Sicras-Mainar et al On the other hand, the use of antipsychotic drugs (APDs) has been increasing considerably during recent years, not only as a result of growth in the population that uses such substances, but also because of expanded use of such medica- tion in other clinical situations in which they are considered to be of potential beneﬁt for patients. However, the evidence to date suggests that antipsychotics, or at least some of the most widely used APDs, are associated with a considerable increase in patient body weight ( 7%) and with the develop- ment of glucose and lipid metabolic alterations. This in turn can imply an increased risk of premature death among such patients due to cardiovascular events (Haupt 2006; Tandon et al 2006; Wu et al 2006). These repercussions are more notorious in the case of second generation APDs (atypical drugs), though the level of risk tends to vary according to the different drug substances used (Babidge et al 2001; Morgan et al 2003; Hiroeh et al 2001). These drugs increase the activity of AMP kinase within the hypothalamus, blocking the activity of the H1 histamine receptors. In this way, a link is established between weight gain and atypical APD use. Although the typical or classical APDs also induce this side effect, the precise mechanism involved in this case is not known (Haupt 2006). Nevertheless, considerable controversy is found among different authors. As an example, clozapine and olanzapine, in addition to the known increases in body weight, can also elevate cholesterol and triglyceride con- centrations (ADA et al 2004; Kane et al 2004; Fenton et al 2006; Pujol-Domenech et al 2006), or increase the risk of developing diabetes mellitus (Aranceta-Bartrina et al 2005; Flores-Meneses et al 2005). Similar results have also been recorded in patients treated with risperidone, though the nega- tive effects upon the health of these subjects are somewhat more controversial. Unfortunately, the role and importance of each of them are often difﬁcult to assess, and it is likewise difﬁcult to determine whether certain biological alterations are the cause or effect of the excess body weight (Jin et al 2004; Dinca et al 2005; Flores-Meneses et al 2005; Haupt 2006; Pujol-Domenech et al 2006; Schneider et al 2006; Woodward et al 2007). The present study further evaluates previously observed associations between obesity and typical and atypical APD use, and explores its inﬂuence upon health care resource utilization in adult outpatients followed-up on by ﬁve primary care teams in the Spanish population setting. Methods A retrospective, multicenter study was conducted based on the medical records of adult patients monitored on an outpatient 220 basis and under normal clinical practice conditions. The study population was seen by ﬁve Primary Care teams managed by Badalona Serveis Assistencials, S.A., and involving a designated recruitment population of about 105,300 inhabit- ants (14.5% over 64 years of age). The designated population is predominantly urban, with middle to low socioeconomic level, and working mainly in the industrial setting. Primary care team organization is of a reformed character, involving public management and the provision of private services (concerted). Badalona Serveis Assistencials S.A. possesses personnel, a training policy, organization model and services offered proﬁle similar to that of most primary care centers in Catalonia, Spain, with decentralized management and single structural services. The study included all patients seen between July 1, 2004 and June 30, 2005, meeting the following criteria: a) age over 18 years; b) initiation of pharmacological treatment with APDs; and c) inclusion in the chronic prescriptions program with regular patient reports for the programmed visits to obtain the corresponding medical prescriptions (with registry of the daily dose, time interval and duration of each treatment). Patients failing to report to the centers were excluded, as were those displaced or outside the zone, and those presenting disabling mental disorders. Obesity was deﬁned as the presence of excess body weight secondary to the accumulation of adipose tissue, with a body mass index (BMI, kg/m2) of over 30 (NCEP 2002). Information was col- lected on the prescription of APDs (atypical: amisulpiride, clozapine, olanzapine, quetiapine, risperidone and zipra- sidone; typical: chlorpromazine, clotiapine, ﬂuphenazine, haloperidol, levomepromazine, perphenazine, periciazine, pimozide, pipothiazine, tiapride, thioproperazine, thiorida- zine, zuclopentixol), reﬂected in the computer-based case histories, according to the recommendations of the pre- scribing physician (WHO 1995). Quantiﬁcation was made of the number of health problems attended per patient/year (comorbidity), considered as a diagnosis-equivalent disease care problem (International Classiﬁcation of Primary Care, ICPC) (Lamberts et al 1993). The personal antecedents were the following: arterial hypertension (K86), dyslipid- emia (T93), diabetes mellitus (T90), active smoking (P17), alcoholism (P15), ischemic heart disease (K74, cardiac isch- emia with angina; K75, acute myocardial infarction; K76, coronary ischemia), cerebrovascular accident (K90, K91), cardiovascular event, chronic obstructive pulmonary disease (R95, chronic airﬂow obstruction) and bronchial asthma (R96). The Charlson Index was quantiﬁed as an estimation of morbidity burden (severity), and the following clinical Neuropsychiatric Disease and Treatment 2008:4(1)