A risk algorithm that predicts alcohol use disorders among college students.

The first year of college may carry especially high risk for onset of alcohol use disorders. We assessed the one-year incidence of alcohol use disorders (AUD) among incoming first-year students, predictors of AUD-incidence, prediction accuracy and population impact. A prospective cohort study of first-year college students (baseline: N = 5843; response rate = 51.8%; 1-year follow-up: n = 1959; conditional response rate = 41.6%) at a large university in Belgium was conducted. AUD were evaluated with the AUDIT and baseline predictors with the Composite International Diagnostic Interview Screening Scales (CIDI-SC). The one-year incidence of AUD was 3.9% (SE = 0.4). The most important individual-level baseline predictors of AUD incidence were being male (OR = 1.53; 95% CI = 1.12-2.10), a break-up with a romantic partner (OR = 1.67; 95% CI = 1.08-2.59), hazardous drinking (OR = 3.36; 95% CI = 1.31-8.63), and alcohol use characteristics at baseline (ORs between 1.29 and 1.38). Multivariate cross-validated prediction (cross-validated AUC = 0.887) shows that 55.5% of incident AUD cases occurred among the 10% of students at highest predicted risk (20.1% predicted incidence in this highest-risk subgroup). Four out of five students with incident AUD would hypothetically be preventable if baseline hazardous drinking was to be eliminated along with a reduction of one standard deviation in alcohol use characteristics scores, and another 15.0% would potentially be preventable if all 12-month stressful events were eliminated. Screening at college entrance is a promising strategy to identify students at risk of transitioning to more problematic drinking and AUD, thus improving the development and deployment of targeted preventive interventions.

Using diffusion MRI data acquired with ultra-high gradient strength to improve tractography in routine-quality data.

The development of scanners with ultra-high gradient strength, spearheaded by the Human Connectome Project, has led to dramatic improvements in the spatial, angular, and diffusion resolution that is feasible for in vivo diffusion MRI acquisitions. The improved quality of the data can be exploited to achieve higher accuracy in the inference of both microstructural and macrostructural anatomy. However, such high-quality data can only be acquired on a handful of Connectom MRI scanners worldwide, while remaining prohibitive in clinical settings because of the constraints imposed by hardware and scanning time. In this study, we first update the classical protocols for tractography-based, manual annotation of major white-matter pathways, to adapt them to the much greater volume and variability of the streamlines that can be produced from today's state-of-the-art diffusion MRI data. We then use these protocols to annotate 42 major pathways manually in data from a Connectom scanner. Finally, we show that, when we use these manually annotated pathways as training data for global probabilistic tractography with anatomical neighborhood priors, we can perform highly accurate, automated reconstruction of the same pathways in much lower-quality, more widely available diffusion MRI data. The outcomes of this work include both a new, comprehensive atlas of WM pathways from Connectom data, and an updated version of our tractography toolbox, TRActs Constrained by UnderLying Anatomy (TRACULA), which is trained on data from this atlas. Both the atlas and TRACULA are distributed publicly as part of FreeSurfer. We present the first comprehensive comparison of TRACULA to the more conventional, multi-region-of-interest approach to automated tractography, and the first demonstration of training TRACULA on high-quality, Connectom data to benefit studies that use more modest acquisition protocols.

[Major depressive episode in college freshmen: prevalence, academic functioning and receipt of treatment]. / Depressieve stoornis bij Belgische eerstejaarsstudenten: voorkomen, academische impact en zorggebruik.

Background Little is known about the epidemiology of Major Depressive Episode (mde) in university students. Aim To investigate the prevalence of mde, psychiatric comorbidity, and the association with academic performance among first-year university students, and to investigate to what extent these students use professional mental health services. Method All first-year students at the ku Leuven (Leuven, Belgium) were invited to complete a computer-assisted survey with a weighted cross-sectional design (N=5,460; response rate corrected for drop-out=51.8%). mde was assessed using the Composite International Diagnostic Interview - Screening Scales (cidi-sc) with dsm-iv criteria. Results We found that 13.6% of first-year students met criteria for a cidi-sc mde in the past year. mde was associated with a wide range of other comorbid disorders (such as generalized anxiety disorder or hypo[mania]) and suicidal thoughts and behaviors. mde was associated with significantly lower academic year percentage (-3.6 to -6.4%) and elevated odds of academic year failure (ors=1.5-2.0). Professional service use was estimated at 21.5%. Conclusion mde is common among first-year university students and is associated with a high degree of psychiatric comorbidity and poor academic performance. It is therefore surprising that so few students actually receive treatment for their psychiatric and emotional problems. Tijdschrift voor Psychiatrie 63(2021)1, 24-31.

Brain function and clinical characterization in the Boston adolescent neuroimaging of depression and anxiety study.

We present a Human Connectome Project study tailored toward adolescent anxiety and depression. This study is one of the first studies of the Connectomes Related to Human Diseases initiative and is collecting structural, functional, and diffusion-weighted brain imaging data from up to 225 adolescents (ages 14-17 years), 150 of whom are expected to have a current diagnosis of an anxiety and/or depressive disorder. Comprehensive clinical and neuropsychological evaluations and longitudinal clinical data are also being collected. This article provides an overview of task functional magnetic resonance imaging (fMRI) protocols and preliminary findings (N = 140), as well as clinical and neuropsychological characterization of adolescents. Data collection is ongoing for an additional 85 adolescents, most of whom are expected to have a diagnosis of an anxiety and/or depressive disorder. Data from the first 140 adolescents are projected for public release through the National Institutes of Health Data Archive (NDA) with the timing of this manuscript. All other data will be made publicly-available through the NDA at regularly scheduled intervals. This article is intended to serve as an introduction to this project as well as a reference for those seeking to clinical, neurocognitive, and task fMRI data from this public resource.

Predicting the incidence of non-suicidal self-injury in college students.

BACKGROUND: Despite increased awareness that non-suicidal self-injury (NSSI) poses a significant public health concern on college campuses worldwide, few studies have prospectively investigated the incidence of NSSI in college and considered targeting college entrants at high risk for onset of NSSI. METHODS: Using data from the Leuven College Surveys (n = 4,565; 56.8%female, Mage = 18.3, SD = 1.1), students provided data on NSSI, sociodemographics, traumatic experiences, stressful events, perceived social support, and mental disorders. A total of 2,163 baseline responders provided data at a two-year annual follow-up assessment (63.2% conditional response rate). RESULTS: One-year incidence of first onset NSSI was 10.3% in year 1 and 6.0% in year 2, with a total of 8.6% reporting sporadic NSSI (1-4 times per year) and 7.0% reporting repetitive NSSI (≥ 5 times per year) during the first two years of college. Many hypothesized proximal and distal risk factors were associated with the subsequent onset of NSSI (ORs = 1.5-18.2). Dating violence prior to age 17 and severe role impairment in daily life were the strongest predictors. Multivariate prediction suggests that an intervention focused on the 10% at highest risk would reach 23.9% of students who report sporadic, and 36.1% of students who report repetitive NSSI during college (cross-validated AUCs = .70-.75). DISCUSSION: The college period carries high risk for the onset of NSSI. Individualized web-based screening may be a promising approach for detecting young adults at high risk for self-injury and offering timely intervention.

The associations between non-suicidal self-injury and first onset suicidal thoughts and behaviors.

BACKGROUND: Theoretical and empirical literature suggests that non-suicidal self-injury (NSSI) is an important correlate of suicide risk. The present study was designed to evaluate: (a) whether NSSI is associated with increased odds of subsequent onsets of suicidal thoughts and behaviors (STB) independent of common mental disorders, (b) whether NSSI is associated with increased risk of transitioning from suicide ideation to attempt, and (c) which NSSI characteristics are associated with STB after NSSI. METHOD: Using discrete-time survival models, based on retrospective age of onset reports from college students (n = 6,393, 56.8% female), we examined associations of temporally prior NSSI with subsequent STB (i.e., suicide ideation, plan, and attempt) controlling mental disorders (i.e., MDD, Broad Mania, GAD, Panic Disorder, and risk for Alcohol Dependence). NSSI characteristics associated with subsequent STB were examined using logistic regressions. RESULTS: NSSI was associated with increased odds of subsequent suicide ideation (OR = 2.8), plan (OR = 3.0), and attempt (OR = 5.5) in models that controlled for the distribution of mental disorders. Further analyses revealed that NSSI was associated with increased risk of transitioning to a plan among those with ideation, as well as attempt among those with a plan (ORs = 1.7-2.1). Several NSSI characteristics (e.g., automatic positive reinforcement, earlier onset NSSI) were associated with increased odds of experiencing STB. LIMITATIONS: Surveys relied on self-report, and thus, there is the potential for recall bias. CONCLUSIONS: This study provides support for the conceptualization of NSSI as a risk factor for STB. Investigation of the underlying pathways accounting for these time-ordered associations is an important avenue for future research.

The prevalence of suicidal thoughts and behaviours among college students: a meta-analysis.

BACKGROUND: Adolescence and young adulthood carry risk for suicidal thoughts and behaviours (STB). An increasing subpopulation of young people consists of college students. STB prevalence estimates among college students vary widely, precluding a validated point of reference. In addition, little is known on predictors for between-study heterogeneity in STB prevalence. METHODS: A systematic literature search identified 36 college student samples that were assessed for STB outcomes, representing a total of 634 662 students [median sample size = 2082 (IQR 353-5200); median response rate = 74% (IQR 37-89%)]. We used random-effects meta-analyses to obtain pooled STB prevalence estimates, and multivariate meta-regression models to identify predictors of between-study heterogeneity. RESULTS: Pooled prevalence estimates of lifetime suicidal ideation, plans, and attempts were 22.3% [95% confidence interval (CI) 19.5-25.3%], 6.1% (95% CI 4.8-7.7%), and 3.2% (95% CI 2.2-4.5%), respectively. For 12-month prevalence, this was 10.6% (95% CI 9.1-12.3%), 3.0% (95% CI 2.1-4.0%), and 1.2% (95% CI 0.8-1.6%), respectively. Measures of heterogeneity were high for all outcomes (I 2 = 93.2-99.9%), indicating substantial between-study heterogeneity not due to sampling error. Pooled estimates were generally higher for females, as compared with males (risk ratios in the range 1.12-1.67). Higher STB estimates were also found in samples with lower response rates, when using broad definitions of suicidality, and in samples from Asia. CONCLUSIONS: Based on the currently available evidence, STB seem to be common among college students. Future studies should: (1) incorporate refusal conversion strategies to obtain adequate response rates, and (2) use more fine-grained measures to assess suicidal ideation.

The 6-month effectiveness of Internet-based guided self-help for depression in adults with Type 1 and 2 diabetes mellitus.

AIM: The aim of this research is to examine the 6-month effects of an Internet-based guided self-help intervention for comorbid depressive symptoms in people with diabetes. METHODS: Participants (n = 260) with Type 1 or 2 diabetes and elevated depressive symptoms [Center for Epidemiological Studies Depression Scale (CES-D) ≥ 23] were randomly assigned to a guided Internet-based self-help intervention or a control condition (treatment as usual + online psychoeducation about depression). The primary outcome was a change in depressive symptom severity (CES-D) from baseline to 6-month follow-up. The secondary outcomes included numbers of people achieving treatment response (reliable change of depressive symptoms) and remission (CES-D ≤ 16), as well as the effects on glycaemic control, diabetes-related emotional distress and diabetes acceptance. Repeated measures analysis of variance examined between-group differences using intent-to-treat principles. RESULTS: Both conditions showed improvements in depression severity: intervention condition, d = 1.48 [95% confidence interval (95% CI): 1.21 to 1.76]; control condition d = 0.55 (95% CI: 0.30 to 0.80). Changes were significantly greater in the intervention condition with a large between-group effect size (d = 0.83, 95% CI: 0.57 to 1.08). Accordingly, effects on response [relative risk (RR) = 2.60 (95% CI: 2.01 to 3.36), P < 0.001] and remission [RR = 3.36 (95% CI: 2.98 to 5.44), P < 0.001] were in favour of the intervention group, as were differences in change in diabetes emotional distress (d = 0.50, 95% CI: 0.04 to 0.54), and physical and mental functioning [Short Form Health Survey (SF-12) Physical d = 0.27 (95% CI: 0.01 to 0.51) and SF-12 Mental d = 0.68 (95% CI: 0.11 to 0.40)]. The intervention group was not superior with regard to glycaemic control, diabetes self-management and diabetes acceptance. CONCLUSIONS: The trial indicates that Internet-based guided self-help treatments for depression in people with diabetes can have sustained effects on depressive symptoms, well-being and emotional distress associated with diabetes.

Psychological interventions to reduce suicidality in high-risk patients with major depression: a randomized controlled trial.

BACKGROUND: Positive psychological constructs have been associated with reduced suicidal ideation, and interventions to cultivate positive feelings have the potential to reduce suicide risk. This study compares the efficacy of a 6-week, telephone-based positive psychology (PP) intervention against a cognition-focused (CF) control intervention among patients recently hospitalized for depression and suicidal ideation or behavior. METHOD: A total of 65 adults with a current major depressive episode reporting suicidal ideation or a recent suicide attempt were enrolled from participating in-patient psychiatric units. Prior to discharge, participants were randomized to the PP (n = 32) or CF (n = 33) intervention. In both interventions, participants received a treatment manual, performed weekly PP (e.g. gratitude letter) or CF (e.g. recalling daily events) exercises, and completed weekly one-on-one telephone sessions over 6 weeks. Between-group differences in hopelessness (primary outcome), depression, suicidality and positive psychological constructs at 6 and 12 weeks were tested using mixed-effects models accounting for intensity of post-hospitalization psychiatric treatment. RESULTS: Compared with PP, the CF intervention was associated with significantly greater improvements in hopelessness at 6 weeks (ß = -3.15, 95% confidence interval -6.18 to -0.12, effect size = -0.84, p = 0.04), but not 12 weeks. Similarly, the CF intervention led to greater improvements in depression, suicidal ideation, optimism and gratitude at 6 and 12 weeks. CONCLUSIONS: Contrary to our hypothesis, the CF intervention was superior to PP in improving hopelessness, other suicide risk factors and positive psychological constructs during a key post-discharge period among suicidal patients with depression. Further study of this CF intervention is warranted in populations at high suicide risk.

First onset of suicidal thoughts and behaviours in college.

BACKGROUND: College students are a worldwide increasing group of young people at risk for suicidal thoughts and behaviours (STB). However, no previous studies have prospectively investigated the first onset of STB during the college period. METHODS: Using longitudinal data from the Leuven College Surveys, 2337 (response rate [RR]=66.6%) incoming freshmen provided baseline data on STB, parental psychopathology, childhood-adolescent traumatic experiences, 12-month risk for mental disorders, and 12-month stressful experiences. A total of 1253 baseline respondents provided data on 12-month STB in a two-year annual follow-up survey (conditional RR=53.6%; college dropout adjusted conditional RR=70.2%). RESULTS: One-year incidence of first-onset STB was 4.8-6.4%. Effect sizes of the included risk factors varied considerably whether viewed from individual-level (ORs=1.91-17.58) or population-level perspective (PARPs=3.4-34.3%). Dating violence prior to the age of 17, physical abuse prior to the age of 17, and 12-month betrayal by someone else than the partner were most strong predictors for first-onset suicidal ideation (ORs=4.23-12.25; PARPs=8.7-27.1%) and plans (ORs=6.57-17.58; PARPs=15.2-34.3%). Multivariate prediction (AUC=0.84-0.91) revealed that 50.7-65.7% of first-onset STB cases were concentrated in the 10% at highest predicted risk. LIMITATIONS: As this is a first investigation of STB onset in college, future studies should use validation samples to test the accuracy of our multivariate prediction model. CONCLUSIONS: The first onset of STB in college appears to be higher than in the general population. Screening at college entrance is a promising strategy to identify those students at highest prospective risk, enabling the cost-efficient clinical assessment of young adults in college.

Mental disorders among college students in the World Health Organization World Mental Health Surveys.

BACKGROUND: Although mental disorders are significant predictors of educational attainment throughout the entire educational career, most research on mental disorders among students has focused on the primary and secondary school years. METHOD: The World Health Organization World Mental Health Surveys were used to examine the associations of mental disorders with college entry and attrition by comparing college students (n = 1572) and non-students in the same age range (18-22 years; n = 4178), including non-students who recently left college without graduating (n = 702) based on surveys in 21 countries (four low/lower-middle income, five upper-middle-income, one lower-middle or upper-middle at the times of two different surveys, and 11 high income). Lifetime and 12-month prevalence and age-of-onset of DSM-IV anxiety, mood, behavioral and substance disorders were assessed with the Composite International Diagnostic Interview (CIDI). RESULTS: One-fifth (20.3%) of college students had 12-month DSM-IV/CIDI disorders; 83.1% of these cases had pre-matriculation onsets. Disorders with pre-matriculation onsets were more important than those with post-matriculation onsets in predicting subsequent college attrition, with substance disorders and, among women, major depression the most important such disorders. Only 16.4% of students with 12-month disorders received any 12-month healthcare treatment for their mental disorders. CONCLUSIONS: Mental disorders are common among college students, have onsets that mostly occur prior to college entry, in the case of pre-matriculation disorders are associated with college attrition, and are typically untreated. Detection and effective treatment of these disorders early in the college career might reduce attrition and improve educational and psychosocial functioning.

The impact of lifetime suicidality on academic performance in college freshmen.

BACKGROUND: While suicidal thoughts and behaviors (STB) among college students are common, the associations between STB and academic performance are not well understood. METHODS: As part of the World Mental Health Surveys International College Student project, web-based self-reported STB of KU Leuven (Leuven, Belgium) incoming freshmen (N=4921; response rate=65.4%) was collected, as well as academic year percentage (AYP), and the departments to which students belong. Single- and multilevel multivariate analyses were conducted, adjusted for gender, age, parental educational level, and comorbid lifetime emotional problems. RESULTS: Lifetime suicide plan and attempt upon college entrance were associated with significant decreases in AYP (3.6% and 7.9%, respectively). A significant interaction was found with average departmental AYP, with STB more strongly associated with reduced AYP in departments with lower than higher average AYP. LIMITATIONS: Limited sample size precluded further investigation of interactions between department-level and student-level variables. No information was available on freshman secondary school academic performance. CONCLUSIONS: Lifetime STB has a strong negative association with academic performance in college. Our study suggests a potential role for the college environment as target for treatment and prevention interventions.

Hematopoietic colony-forming cells derived from human embryonic stem cells.

Human embryonic stem (ES) cells are undifferentiated, pluripotent cells that can be maintained indefinitely in culture. Here we demonstrate that human ES cells differentiate to hematopoietic precursor cells when cocultured with the murine bone marrow cell line S17 or the yolk sac endothelial cell line C166. This hematopoietic differentiation requires fetal bovine serum, but no other exogenous cytokines. ES cell-derived hematopoietic precursor cells express the cell surface antigen CD34 and the hematopoietic transcription factors TAL-1, LMO-2, and GATA-2. When cultured on semisolid media with hematopoietic growth factors, these hematopoietic precursor cells form characteristic myeloid, erythroid, and megakaryocyte colonies. Selection for CD34(+) cells derived from human ES cells enriches for hematopoietic colony-forming cells, similar to CD34 selection of primary hematopoietic tissue (bone marrow, umbilical cord blood). More terminally differentiated hematopoietic cells derived from human ES cells under these conditions also express normal surface antigens: glycophorin A on erythroid cells, CD15 on myeloid cells, and CD41 on megakaryocytes. The in vitro differentiation of human ES cells provides an opportunity to better understand human hematopoiesis and could lead to a novel source of cells for transfusion and transplantation therapies.

Determination of pesticides in soil samples by supercritical fluid chromatography-atmospheric pressure chemical ionisation mass spectrometric detection.

This paper presents an analytical technique for the determination of pesticides in soil by packed-column supercritical fluid chromatography interfaced with atmospheric pressure chemical ionisation mass spectrometry (pSFC-APCI-MS). The technique provides a versatile method for the detection and quantification of pesticides belonging to three different commonly used classes, triazines (ametryne, atrazine), carbamates (carbofuran) and sulfonylureas (chlorsulfuron, metsulfuron methyl and benzsulfuron methyl). The APCI mass spectra for all the pesticides studied consisted of protonated molecule ions as the most abundant ion at low cone voltages, except for metsulfuron methyl and benzsulfuron methyl, which gave a fragment ion as the most abundant ion with the protonated molecule ion at low intensity. Increasing the cone voltage provided informative fragmentation patterns for all species. The technique shows good linearity over the concentration range of 0.1-50 micrograms ml-1, with r2 values as follows: atrazine 0.997, ametryne 0.995, carbofuran 0.999, benzsulfuron methyl 0.999, chlorsulfuron 0.995 and metsulfuron methyl 0.997. The detection limits in the selected ion mode were atrazine 201, ametryne 144 and carbofuran 385 pg, which were calculated by using the standard solution, and benzsulfuron methyl 2.045, chlorsulfuron 1.435 and metsulfuron methyl 2.414 ng, which were determined by using spiked soil samples. The pSFC-MS system was shown to have a high degree of reproducibility. The technique was then applied to the determination of the above pesticides in soil samples. The results obtained show that there is no matrix effect from the soil and that the detection limits for all pesticides in soil were similar to those found for the standard solutions.

Direct and indirect costs of rheumatoid arthritis to an employer.

This study is among the first to estimate the overall economic burden of rheumatoid arthritis (RA) from an employer perspective. The annual, per capita cost of RA was determined for beneficiaries of a major employer by analyzing medical, pharmaceutical, and disability claims data. The incremental costs related to RA were determined by matching RA patients to a case-control group of individuals with no recorded RA treatment. The utilization of health care services as well as the rate of disability among RA patients was substantially higher than among the controls. For example, annual, per capita employer expenditures for RA employees with disability were almost 3 times those for their controls ($17,822 vs $6131, respectively). Treatment to address not only the severity but also the progression of RA may substantially reduce overall employer expenditures for this disease.

SFC/FTIR, SFC/APCI-MS and MALDI-TOF-MS for the analysis of siloxane-ethylene oxide copolymers.

Polydimethylsiloxanes (PDMSs) modified by introducing ethylene oxide units with the aim of forming sufficiently water-soluble siloxane compounds were characterized using supercritical fluid chromatography (SFC) coupled with Fourier transform infrared (FTIR) spectroscopy and atmospheric pressure chemical ionization mass spectrometry (APCI-MS), and matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS). SFC has a domain in analyzing oligomers. Hyphenated techniques enable elucidation of the components. Remarkable is the resolution and short analysis time of MALDI-TOF-MS. SFC also allows quantification of the basic and reaction products.

Characterization of varietal differences in essential oil components of hops (Humulus lupulus) by SFC-FTIR spectroscopy.

A supercritical fluid chromatographic method combined with Fourier-transform infrared spectroscopy detection (SFC-FTIR) was developed for determination of varietal differences in essential oil constituents in hops (Humulus lupulus). Infrared spectra (IR) of the major constituents of essential oil of hops were taken as films deposited on AgCl discs and compared with those obtained after chromatographic separation in the IR flow-cell with supercritical carbon dioxide (scCO2). Spectra from AgCl discs were comparable to those in scCO2, but in scCO2 most of the bands appeared approximately 8-10 cm-1 to higher wave numbers. Open-tubular SFC-FTIR analysis of the essential oil of 4 different hop varieties was performed. The SFC-FTIR chromatograms showed differences in the location and relative intensity of the peaks depending on the variety, which was further confirmed by consideration of their FTIR spectra.

An in vivo function for the transforming Myc protein: elicitation of the angiogenic phenotype.

The ability of neoplastic cells to recruit blood vasculature is crucial to their survival in the host organism. However, the evidence linking dominant oncogenes to the angiogenic switch remains incomplete. We demonstrate here that Myc, an oncoprotein implicated in many human malignancies, stimulates neovascularization. As an experimental model, we used Rat-1A fibroblasts that form vascular tumors upon transformation by Myc in immunocompromised mice. Our previous work and the use of neutralizing antibodies reveal that in these cells, the angiogenic switch is achieved via down-modulation of thrombospondin-1, a secreted inhibitor of angiogenesis, whereas the levels of vascular endothelial growth factor, a major activator of angiogenesis, remain high and unaffected by Myc. Consistent with this finding, overexpression of Myc confers upon the conditioned media the ability to promote migration of adjacent endothelial cells in vitro and corneal neovascularization in vivo. Furthermore, mobilization of estrogen-dependent Myc in vivo with the appropriate steroid provokes neovascularization of cell implants embedded in Matrigel. These data suggest that Myc is fully competent to trigger the angiogenic switch in vivo and that secondary events may not be required for neovascularization of Myc-induced tumors.

Angiogenesis assays: problems and pitfalls.

Many studies of angiogenesis inducers and inhibitors rely on in vitro or in vivo models as indicators of efficacy. However, as valuable as these models are, there are limitations to each one of these. This overview describes some of the principal methods now in use and discusses the advantages and some of the limitations of these methods. It is suggested that multiple assays, involving both in vitro and in vivo assays, are at present the best way to minimize the problems inherent in any specific assay.