Developmental trajectories of adolescent cannabis use and their relationship to young adult social and behavioural adjustment: a longitudinal study of Australian youth

This study aimed to identify distinct developmental trajectories (sub-groups of individuals who showed similar longitudinal patterns) of cannabis use among Australian adolescents, and to examine associations between trajectory group membership and measures of social and behavioural adjustment in young adulthood. Participants (n=852, 53% female) were part of the International Youth Development Study. Latent class growth analysis was used to identify distinct trajectories of cannabis use frequency from average ages 12 to 19, across 6 waves of data. Logistic regression analyses and analyses of covariance were used to examine relationships between trajectory group membership and young adult (average age: 21) adjustment, controlling for a range of covariates. Three trajectories were identified: abstainers (62%), early onset users (11%), and late onset occasional users (27%). The early onset users showed a higher frequency of antisocial behaviour, violence, cannabis use, cannabis-related harms, cigarette use, and alcohol harms, compared to the abstinent group in young adulthood. The late onset occasional users reported a higher frequency of cannabis use, cannabis-related harms, illicit drug use, and alcohol harms, compared to the abstinent group in young adulthood. There were no differences between the trajectory groups on measures of employment, school completion, post-secondary education, income, depression/anxiety, or alcohol use problems. In conclusion, early onset of cannabis use, even at relatively low frequency during adolescence, is associated with poorer adjustment in young adulthood. Prevention and intervention efforts to delay or prevent uptake of cannabis use should be particularly focussed on early adolescence prior to age 12.

Problem gambling patterns among Australian young adults: associations with prospective risk and protective factors and adult adjustment outcomes

There is instability in the developmental course of problem gambling [PG] over time; however, studies that examine PG at an aggregate level obscure these variations. The current study employed data from a longitudinal study of Australian young adults to investigate: 1) PG patterns (i.e., resistance, persistence, desistence, and new incidence); 2) prospective risk and protective factors for these patterns; and 3) behavioural outcomes associated with these patterns. A sample of 2261 young adults (55.73% female) from Victoria, Australia, who were part of the International Youth Development Study completed a survey in 2010 (T1, age 21) and 2012 (T2, age 23) measuring PG (two items based on established measures), risk and protective factors, and behavioural outcomes. The majority of the sample (91.69%) were resistors (no PG at T1 and T2), 3.62% were new incidence PG cases, 2.63% were desistors (PG at T1 but not T2), and 2.07% reported persistent PG at T1 and T2. Individual civic activism was protective of new incidence PG, while affiliation with antisocial peers and frequent alcohol use increased the risk of persistence. Persistent problem gamblers also experienced the greatest number of poor behavioural outcomes at T2. New incidence was associated with internalising symptoms at T2, while desistance was not associated with any behavioural outcomes. In conclusion, each PG pattern was associated with different predictors and outcomes, highlighting the need to consider variation in the course of young adult PG in order to provide efficacious prevention and intervention approaches, and to protect against relapse.

Higher adherence to the Australian dietary guidelines is associated with better mental health status among Australian adult first-time mothers

Background: Mental health disorders are a leading cause of disability worldwide, including in first-time mothers. Understanding the associations between diet and depressive symptoms could assist in improving mental health status in this group. Objective: Our aim was to determine the association between diet quality, fruit, vegetable, and fish consumption and depressive symptoms in first-time mothers aged 19 to 45 years.

Design: We analyzed cross-sectional, baseline data (3 months postpartum) from the Melbourne InFANT (Infant Feeding, Activity, and Nutrition Trial) Extend Program.

Participants/setting: Participants were first-time Australian mothers aged 19 to 45 years from the Geelong and Melbourne regions of Victoria, Australia (n=457).

Main outcome measures: A self-administered, 137-item food frequency questionnaire assessed dietary intake over the past year. Adherence to the 2013 Australian Dietary Guidelines was assessed using the Dietary Guideline Index as a measure of diet quality. Depressive symptoms were determined using the Center for Epidemiologic Studies Depression Scale.

Statistical analysis performed: Relationships between diet quality, fruit, vegetable, and fish intake and depressive symptoms were investigated using linear regression adjusted for relevant covariates (age, smoking status, sleep quality, education, physical activity status, and body mass index).

Results: Better diet quality, as indicated by a higher score on the Dietary Guideline Index, was associated with lower depressive symptoms after adjusting for relevant covariates (β=-.034; 95% CI -.056 to -0.012). There were no other associations between dietary intake and depressive symptoms.

Conclusions: Adherence to the Australian Dietary Guidelines was associated with better mental health status among first-time mothers. Further research, including longitudinal and intervention studies, are required to determine causality between dietary intake and depressive symptoms, which might help inform future public health nutrition programs for this target group.

Adult Autism Spectrum Disorder and intimate relationships

 This thesis investigated the link between ASD traits and relationship development and experience in both adults with ASD and their TD partners, through a series of online questionnaires. Firstly, for a large sample of female and male adults with ASD, we found that poor relationship development outcome was predicted by higher severity of social skills impairment. When males and females were considered separately, we found that higher severity of communication deficits predicted poor relationship development outcome for males only, and higher severity of social skills deficits predicted poor relationship development outcome for females only. We also found that higher severity of circumscribed interests predicted better relationship development outcomes for the whole sample. Next, in a comparison of relationship functioning across three partner groups (TD partners within a TD/TD dyad, ASD partners within an ASD/TD dyad and TD partners within an ASD/TD dyad), findings indicated that TD partners within an ASD/TD dyad had the poorest relationship outcome. Lastly, we investigated actor and partner effects of ASD traits on relationship outcome for a sample of ASD/TD dyads using an APIM. We found minimal evidence to suggest that ASD traits negatively impact relationship outcome of ASD/TD dyads. However, we consistently found that TD partner’s ASD trait severity positively influenced both ASD and TD partner’s relationship outcome, suggesting that mutual understanding between partners is protective against the challenges faced within ASD/TD relationships.