T he Diagnostic and Statistical Manual of Mental Disorders (DSM) provides a common language for mental health professionals and enhances the reliability of diagnoses; however, it does have its limitations. Notably, there is little basis for its current categorical representation of diagnostic entities.In this volume, Schmidt, Kotov, and Joiner present a much needed, alternative approach to developing the DSM-taxometrics, an applied data-analysis tool that discerns categories from continua and establishes defining indicators of identified categories. Integrating the work of Paul Meehl and colleagues, the book begins the ambitious task of "true diagnostics," that is, the application of taxometrics to psychopathological syndromes. In the book, the authors review what is known about the categorical nature of diagnoses, provide a user-friendly primer about taxometrics, and describe the methodology for applying taxometric procedures to diagnostic categories in the DSM. This provocative book will be of interest to any mental health professional who is committed to the refinement of diagnostic procedures.

Objective The authors examined the relationship between cannabis use and the course of illness in schizophrenia over 10 years following first psychiatric hospitalization. Method We assessed 229 patients with a schizophrenia-spectrum disorder five times: during the first admission, and 6 months, 2 years, 4 years, and 10 years later. Ratings of cannabis use and psychiatric symptoms (psychotic, negative, disorganized, and depressive) were made at each assessment. Results The lifetime rate of cannabis use was 66.2%, and survival analysis revealed that this usage was associated with an earlier onset of psychosis. The rates of current use ranged from 10% to 18% across assessments. Cannabis status was moderately stable, with concordance between waves ranging rtet = 0.48 – 0.78. Mixed-effects logistic regression revealed that changes in cannabis use were associated with changes in psychotic symptoms over time even after gender, age, socio-economic status, other drug use, antipsychotic medication use, and other symptoms were controlled. Structural equation modeling indicated that the association with psychotic symptoms was bi-directional. Conclusions Cannabis use is associated with an adverse course of psychotic symptoms in schizophrenia, and vice versa, even after taking into account other clinical, substance, and demographic variables. The specificity of this relationship suggests that clinical interventions to reduce cannabis use may be best targeted at individuals with prominent psychotic symptoms.

Using taxometric procedures, the latent structure of psychopathy was investigated in two studies of children and adolescents. Prior studies have identified a taxon (i.e., a natural category) associated with antisocial behavior in adults as well as children and adolescents. However, features of this taxon suggest that it is not psychopathy but rather a broader class consistent with the construct of life course persistent antisocial behavior. Because the only prior study of youth used a non-clinical sample, the base rate of psychopathy may have been too low to reveal a psychopathy taxon, especially against the background of a broader and more prevalent antisocial behavior taxon. Therefore, this investigation sought to increase the likelihood of finding a psychopathy taxon (should one exist) by increasing its expected base rate through inclusion of clinical cases in the samples studied. Results produced evidence for both a broad antisocial behavior problem taxon consistent with past research and a much lower base rate taxon consistent with prevalence expectations for psychopathy. These findings support the existence of latent taxa for both psychopathy and a broader class of antisocial behavior problems. Further taxometric research appears to be warranted, which should use a broader array of indicators, with greater specificity to psychopathy.

Little is known about the longitudinal relationship of hopelessness to attempted suicide in psychotic disorders. The present study addresses this gap by assessing hopelessness and attempted suicide at multiple time-points over 10-years in a first-admission cohort with psychosis (n=414). Approximately 1 in 5 participants attempted suicide during the 10-year follow-up, and those who attempted suicide scored significantly higher at baseline on the Beck Hopelessness Scale. In general, a given assessment of hopelessness (i.e., baseline, 6-months, 24-months, and 48-months) reliably predicted attempted suicide up to 4–6 years later, but not beyond. Structural equation modeling indicated that hopelessness prospectively predicted attempted suicide even when controlling for previous attempts. Notably, a cut-point of 3 or greater on the Beck Hopelessness Scale yielded sensitivity and specificity values similar to those found in non-psychotic populations using a cut-point of 9. Results suggest that hopelessness in individuals with psychotic disorders confers information about suicide risk above and beyond history of attempted suicide. Moreover, in comparison to non-psychotic populations, even relatively modest levels of hopelessness appear to confer risk for suicide in psychotic disorders.