Le début de l’adolescence est une période de changements rapides où la détresse psychologique et l’expérimentation de la marijuana sont choses fréquentes. Certaines études longitudinales ont démontré que ces deux phénomènes ont tendance à se manifester conjointement tandis que d’autres n’ont pu observer de tel lien. Ces résultats divergents suggèrent que plusieurs questions persistent concernant la nature de cette relation. Cette thèse a pour objectif d’explorer la consommation de marijuana et la détresse psychologique en début d’adolescence afin de mieux saisir les changements à travers le temps, ainsi que d’examiner si ces deux problématiques évoluent conjointement et s’influencent réciproquement. Un échantillon de 448 adolescents garçons et filles fréquentant deux écoles secondaires de Montréal, ont été suivi de secondaire I à secondaire III. De 1999 à 2001, les participants ont complété un questionnaire à chaque année de l’étude incluant des mesures portant sur la consommation de marijuana et la détresse psychologique (IDPESQ-14). Un modèle de mixture semi-paramétrique (Nagin, 2005) a été utilisé afin d’identifier les trajectoires développementales de la consommation de marijuana et de détresse psychologique. Des analyses ont également été effectuées afin d’établir les liens d’appartenance entre chacune des trajectoires de consommation identifiées et la détresse psychologique lors de la première année de l`étude, ainsi qu’entre chacune des trajectoires de détresse psychologique et la consommation de marijuana en première année du secondaire. Finalement, des analyses de trajectoires jointes ont été effectuées afin de déterminer l’interrelation entre la consommation de marijuana et la détresse psychologique. Les résultats de notre étude suggèrent qu’il existe une grande hétérogénéité au niveau de la consommation de marijuana et la détresse psychologique. Trois trajectoires développementales ont été identifiées pour la consommation de marijuana: consommation légère, consommation grandissante et consommation élevée et stable. Trois trajectoires ont également été observées pour la détresse psychologique : basse, moyenne et élevée. Nos résultats démontrent la présence d’un lien entre la détresse psychologique rapportée lors de la première année de l’étude et les trajectoires de consommation problématiques. Ce lien a également été observé entre la consommation de marijuana rapportée lors de première année de l’étude et les trajectoires problématiques de détresse psychologique. Les analyses de trajectoires jointes démontrent la présence d’une concordance entre la consommation de marijuana et la détresse psychologique. Cette interrelation est toutefois complexe puisque les trajectoires de détresse psychologique élevée sont associées à un niveau de consommation de marijuana plus problématique mais l’inverse de cette association est moins probable. Notre étude met en lumière la nature asymétrique de la concordance entre la consommation de marijuana et la détresse psychologique. / Early adolescence is period of rapid changes where psychological distress and marijuana use experimentation are common occurrences. Longitudinal studies examining the association between these two phenomena have provided mixed results and many questions prevail regarding the nature of this association. The purpose of this study is to examine the patterns of co-occurrence between marijuana use and psychological distress in early adolescence. A sample of 448 adolescent boys and girls attending two high schools in Montreal, Canada was followed from Grade 7 to 9. From 1999 to 2001, the participants completed an annual survey which included measures of marijuana use and psychological distress (IDPESQ-14). Using a semi-parametric group based modeling strategy, the study has for objectives to establish the developmental trajectories of marijuana use and psychological distress in early adolescence, to explore how marijuana use or psychological distress measured at baseline is associated with various developmental trajectories and to examine the interrelationship of these two phenomena as they concurrently develop over the span of our study. Our results provide evidence that marijuana use and psychological distress are phenomena with great heterogeneity as they develop over time. We identified 3 trajectories of marijuana use: Light Users, Increasers and High Chronics and 3 trajectories of psychological distress: Low, Medium and High. Our findings also demonstrate that adolescents who reported psychological distress at baseline were more likely to follow problematic trajectories of marijuana use when compared to light users and the reverse of the association was also true since adolescent who reported marijuana use at baseline were more likely to follow an elevated trajectory of psychological distress. Our joint trajectory analysis demonstrated that the developmental patterns of co-occurrence of marijuana use and psychological distress are complex. Our study provides evidence that adolescents following a trajectory of elevated psychological distress are at increased risk of also following a trajectory of elevated marijuana use but adolescents following a problematic trajectory of marijuana use are not necessarily at greater risk of following an elevated trajectory of psychological distress. Our study highlights the presence of an asymmetrical relationship between marijuana use and psychological distress in early adolescence.

Postpartum depression is an illness that is frequently unreported and undetected for a variety of reasons and may be potentially devastating for the mother affected as well as her family. Routine screening of postpartum women enables health practitioners to detect symptoms of PPD early and provides an opportunity for early intervention which may improve the outcome and increase the mother’s chances of an earlier recovery. It is therefore important that reliable and convenient screening tools are available to health practitioners who have contact with postpartum women. The primary objective of this research was to make an Afrikaans version of an existing screening scale available – the Postpartum Depression Screening Scale (PDSS), designed specifically to encompass the multifaceted phenomenon of PPD. In accordance with this objective, the validity and reliability of the PDSS and its Afrikaans version was investigated in English- and Afrikaans-speaking South African mothers. A further objective of this study was to compare the performance of the PDSS with the Edinburgh Postnatal Depression Scale (EPDS) and the Quick Inventory of Depressive Symptomatology (QIDS-SR16). Various factors have been reported to be associated with the development of PPD. The final objective of this study was to explore the relationship between known risk factors for PPD and high scores on the PDSS amongst women in South African. A total of 365 South African mothers, between 4 and 16 weeks postpartum participated in this study. English-speaking mothers (n = 187) completed the PDSS, EPDS, QIDS, and a demographic and psychosocial questionnaire, while Afrikaans speaking mothers (n = 178) completed the respective Afrikaans versions of these questionnaires. A multiple translation method – Brislin’s back-translation method and the committee approach – was used to translate the PDSS and the QIDS into Afrikaans. An item response theory (IRT), Rasch analysis, was used to examine dimensionality, item difficulty, differential item functioning, and category functioning of the PDSS and the Afrikaans PDSS. Results reveal excellent person reliability estimates for the Afrikaans PDSS as well as for the PDSS in a South African sample. Both language versions performed reasonably well and the majority of items in the PDSS dimensions and the Afrikaans PDSS dimensions demonstrated fit statistics that supported the underlying constructs of each dimension. Some items were identified as problematic, namely Item 2, Item 25, Item 28, and Item 30. The item person construct maps show reasonably good spread of items. There were, however, persons that scored higher than the items could measure and an overrepresentation of items at the mean level. The Likert response categories proved to be effective for all the Afrikaans PDSS items and almost all the PDSS items. Results indicate that 49.7% of mothers screened positive for major PPD using the PDSS. A further 17.3% of mothers obtained scores indicating the presence of significant symptoms of PPD. Statistically significant correlations were obtained between total scores on the PDSS, the EPDS, and the QIDS-SR16. Stepwise multiple regression analysis identified 11 variables that were significantly associated with a high PDSS total score. These were a history of psychiatric illness, postpartum blues, feeling negative or ambivalent about expecting this baby, fearful of childbirth, infant temperament, antenatal depression in recent pregnancy, lack of support from the baby’s father, concern about health related issues regarding the infant, lack of support from friends, difficulty conceiving, and life stress. / Thesis (PhD)--University of Pretoria, 2012. / Psychology / unrestricted