501. Head Injury, Race, and Substance Abuse in Psychiatric Patients William B. Lawson1, Steve Arndt2, Steve Fleck3, Steve Strakowski3, Tanya Seaward1, Patient Characteristics Study Group, Shanique Cartwright1 1Psychiatry and Behavioral Sciences, Howard University, Washington, DC, 2Psychology, University of Iowa, Iowa City, IA, 3Psychiatry, University of Cincinnati, Cincinnati, OH Background: Head injury (HI) has been associated with neuropsychiatric disorders including affective disorders and psychosis. HI is believed to be more common in ethnic minorities and/or those from a low socioeconomic class. HI may contribute to ethnic differences in prevalence and misdiagnosis of mental disorders. Methods: We examined HI in a study assessing ethnic differences in treatment seeking psychiatric patients with an affective disorder, psychotic disorder, or both. Any reports of ethnic differences in head injury may be a consequence of ethnic differences in substance abuse and dependence and its relation to head trauma. Results: 532 patients were evaluated and 136 (26%) had HI present. 217 (41%) were African American, 127 (24%) were Latino, and 188 (35%) were White. Latino subjects reported the highest occurrence of HI (39%), followed by Whites (28%) and African Americans (16%).African Americans had significantly fewer head injuries then either Latinos or Whites which did not differ significantly from each other. With logistic regression adjusting for race/ ethnic group, age, and the presence or absence of substance abuse, the ethnicity differences in HI disappeared, However the race by substance abuse interaction attained significance. Conclusions: Any reports of ethnic differences in head injury may be a consequence of ethnic differences in substance abuse and dependence and its relation to head trauma. Supported by RO1MH68797-01A2. 751. Major Depressive Disorders and Serum Cortisol Secretion: A Random Effect Meta-Analysis Malena A. Banks, William B. Lawson, Evaristus A. Nwulia Department of Psychiatry, Howard University Hospital, Washington, DC Background: Although subtypes of Major Depressive Disorders (MDD) have been associated with HPA axis activity, the literature on utility of cortisol measures as biomarkers of MDD has been mixed. We combined published comparative studies of serum cortisol concentrations between depressed and non-depressed subjects, using random effects meta-analysis, which accounts for observed and un-observed heterogeneity to obtain an overall estimate of the association between MDD and serum cortisol. Methods: We searched major databases (MEDLINE, PsycINFO and Cochrane) for comparative studies published from January 1, 1988 - September 10, 2008; manual journal searches; reference list reviews; and citation tracking of included articles. We included studies written in English, restricted to human populations, which obtained any measure of serum cortisol level in depressed subjects and either healthy or non-depressed psychiatric controls. Results: We have identified 58 studies meeting our research criteria; these included a total of 2735 individuals. The mean cortisol concentration (± S.D.) for the total study sample is 81.22 (± 6.72) μg/l; the mean effect of depression (± S.D) = 19.6 (± 4.6) μg/l (P < 0.00001). Depression accounted for 76% of the variance in serum cortisol level across studies. Conclusions: This study reveals strong association between serum cortisol and MDD, and provides further support for the incorporation of cortisol measure or other more specific measures of HPA activity as a biomarker of MDD. Our discussion focuses on subtypes of depression with the strongest association with hypercortisolism as well as other factors accounting for heterogeneity in reviewed studies.