Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Thomas Joiner, Florida State University, College of Arts and Sciences, Dept. of Psychology. Title and description from dissertation home page (viewed Sept. 15, 2006). Document formatted into pages; contains v, 35 pages. Includes bibliographical references.

Thesis (M.A.)--Lancaster Bible College, 2003. / Includes bibliographical references (leaves 48-50).

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisors: Stephanie S. Rude and James W. Pennebaker. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

The prevalence and nature of depression among adolescents in the general population has received considerable empirical attention in the last decade. Although researchers and clinicians agree that depressive symptoms and depressive disorders are distressing to youths and may have wide ranging effects on their health and development, specific features of depression noted during adolescence (e.g., different manifestations of symptoms) warrant further examination. Using the domain of developmental psychopathology as a conceptual framework, the present study (a) examined sex and age differences in adolescents’ reports of depressive symptoms; (b) explored the extent to which other symptoms were associated with adolescents’ depressive symptoms; and (c) identified subtypes of adolescents who manifested their symptoms of depression in different ways. Data were collected from 379 community-dwelling adolescents (193 females, 186 males) ranging in age from 12 to 19 years. During one class period, youths completed anonymous questionnaires assessing their depressive and comorbid symptoms, personality style, and relationships with their mothers and fathers. Descriptive analyses showed that adolescent females reported higher levels of depressive symptoms than adolescent males and that adolescents’ reports of depressive symptoms tended to show a linear increase across age. Correlational analyses revealed that females who reported depressive symptoms were likely to also report anxiety symptoms whereas males who reported depressive symptoms also reported symptoms of anxiety, substance use, school misconduct, and antisocial behaviour. A K-means cluster analysis of the MAPI personality scales identified three subtypes of adolescents who manifested their depressive symptoms in different ways. These subtypes were labelled Isolated-Discontented, Engaged-Intrusive, and Inhibited- Insecure and were distinguished by their levels of depressive symptoms, patterns of co-occurring symptoms, relationships with their mothers, adolescent-specific concerns (e.g., personal esteem), and behavioural correlates (e.g.. impulse control). The discussion focuses on the clinical implications of these subtypes of depressed adolescents (e.g.. their clinical presentation, need for treatment, and appropriateness of specific interventions) as well as factors that may be contributing to the high level of depressive symptoms reported by the adolescents in this sample. / Graduate

Inaugural lecture delivered at Rhodes University. / Rhodes University Libraries (Digitisation)

M.A. (Psychology) / Please refer to full text to view abstract

Diagnosis of Major Depressive Disorder (MDD) is currently symptom-based and no externally validated tests are available for routine use to confirm clinical diagnoses. Eye movement abnormalities in schizophrenia (SCZ) and bipolar disorder (BPAD) have been consistently reported and their potential as a biological trait marker highlighted. Only a limited amount of research has been conducted in MDD. Eye movement performance of MDD patients (n = 99; F:M = 55:44; Mdn age = 48) was investigated using picture free-viewing, smooth pursuit and fixation stability tasks and recorded using a non-invasive EyeLink1000 infra-red eye tracker. Performance was compared with identical measures from SCZ, BPAD, Primary Care depression (DEP) and control participants. Analysis was conducted using analyses of variance and machine learning using Probabilistic Neural Networks (PNN). We discovered a unique MDD specific eye movement phenotype, which differentiated patients with MDD from other diagnostic groups with remarkable accuracy. MDDs generated a markedly poor smooth pursuit performance, characterised by small signal-to-noise ratio, small tracking gain and large positional error. Patients also exhibited a slow average saccade velocity during free-viewing and pursuit, and poor fixation maintenance on a centralised target. A PNN classifier delineated MDD from controls with exceptional statistical sensitivity (100%) and specificity (99%), independent of state or demographics. MDD was delineated from SCZ and BPAD in all models with above 89% sensitivity and 95% specificity. MDD and DEP patients were delineated with remarkable statistical sensitivity (90%) and specificity (98%). This emerging evidence suggests possible subtypes consistent with clinical features. Testretest reliability was high for a majority of performance measures; however some measures were less robust. Brief neuropsychology assessment advocated the role of frontal lobes in oculomotor behaviour. This preliminary evidence argues for a specific MDD oculomotor dysfunction and represents potential for a diagnostically applicable biological trait marker.