Vegetarianism and mental health: Evidence from the 1970 British Cohort Study.

BACKGROUND: Reducing animal product consumption has benefits for population health and the environment. The relationship between vegetarianism and mental health, however, remains poorly understood. This study explores this relationship in a nationally representative cohort in Great Britain. METHODS: We use data from the 1970 British Cohort Study, which collected information on vegetarianism at age 30 in 2000 (n = 11,204) and psychological distress (PD) at ages 26, 30, 34, 42, and 46-48 in 2016/18. We first developed a statistical adjustment strategy by regressing PD at age 30 on vegetarianism and 14 confounders measured at ages 10 and 26. We then ran multilevel growth curve models, testing whether within-person changes in PD between ages 30 and 46-48 differed by vegetarianism, before and after statistical adjustment. RESULTS: At age 30, 4.5 % of participants reported being vegetarian. In the cross-sectional models at age 30, vegetarians reported more distress compared with non-vegetarians in bivariate analysis (b = 0.30, 95%CI 0.09, 0.52), but this difference disappeared in the fully-adjusted model (b = 0.02, 95%CI -0.17, 0.21). In the longitudinal models between ages 30 and 46/48, there were no differences in within-person changes in psychological distress between vegetarians and non-vegetarians (p = .723). Sensitivity analyses using red meat consumption yielded similar findings. CONCLUSION: In this British cohort, vegetarianism at age 30 was not associated with changes in psychological distress during mid-adulthood. Since psychological distress in early adulthood predicted vegetarianism at age 30, more studies are needed to disentangle the progression of this relationship over the life-course.

Differential stress response to psychological and physical stressors in children using spatial versus response-dependent navigation strategies.

Previous work from our lab has shown that basal cortisol levels are different between healthy young adults who spontaneously use caudate nucleus-dependent response strategies compared to young adults who use hippocampus-dependent spatial navigation strategies. Young adults who use caudate nucleus dependent strategies display lower basal cortisol levels compared to those who use hippocampus-dependent strategies. In the current study, we assessed navigation strategies in children using a virtual navigation task and measured cortisol at baseline as well as cortisol reactivity to both a psychological and to a physical stressor. Replicating what is observed in adults, we found that children who used caudate nucleus-dependent navigation strategies displayed lower cortisol levels at baseline compared to those who used hippocampus-dependent strategies. The psychological stressor, knowledge that a blood draw would be performed by a nurse, caused a significant increase in cortisol uniquely in response learners. The physical stressor, the actual blood draw, produced a significant increase in cortisol amongst spatial learners that was then comparable to levels observed in response learners. Lower baseline cortisol and higher cortisol psychological stress response observed amongst children who used response strategies may therefore reflect early biological changes during development which may have an impact later in life when considering risk for neuropsychiatric disorders.

Opposing effects of cortisol on learning and memory in children using spatial versus response-dependent navigation strategies.

Previous studies showed that healthy young adults who spontaneously use caudate nucleus-dependent strategies on a virtual navigation task, have significantly lower basal levels of cortisol compared with adults who use hippocampus-dependent spatial navigation strategies. In the current paper, we assessed the relation between basal cortisol levels and learning using a virtual navigation task in children. We show that basal cortisol level has a differential effect on learning and memory between children using spatial and response navigation strategies. Specifically, cortisol was found to be beneficial for learning performance in children using spatial strategies, such that higher levels of cortisol were associated with more efficient learning in a virtual maze. In contrast, cortisol had a deleterious effect on learning the virtual maze in children using response strategies, such that higher cortisol levels were associated with increased spatial working memory errors. Based on these results, individual differences in navigation strategy could help explain contradictory results in the literature showing that cortisol can have either a positive or negative association with learning and memory performance.

Virtual navigation strategies from childhood to senescence: evidence for changes across the life span.

This study sought to investigate navigational strategies across the life span, by testing 8-years old children to 80-years old healthy older adults on the 4 on 8 virtual maze (4/8VM). The 4/8VM was previously developed to assess spontaneous navigational strategies, i.e., hippocampal-dependent spatial strategies (navigation by memorizing relationships between landmarks) versus caudate nucleus-dependent response strategies (memorizing a series of left and right turns from a given starting position). With the 4/8VM, we previously demonstrated greater fMRI activity and gray matter in the hippocampus of spatial learners relative to response learners. A sample of 599 healthy participants was tested in the current study. Results showed that 84.4% of children, 46.3% of young adults, and 39.3% of older adults spontaneously used spatial strategies (p < 0.0001). Our results suggest that while children predominantly use spatial strategies, the proportion of participants using spatial strategies decreases across the life span, in favor of response strategies. Factors promoting response strategies include repetition, reward and stress. Since response strategies can result from successful repetition of a behavioral pattern, we propose that the increase in response strategies is a biological adaptive mechanism that allows for the automatization of behavior such as walking in order to free up hippocampal-dependent resources. However, the down-side of this shift from spatial to response strategies occurs if people stop building novel relationships, which occurs with repetition and routine, and thereby stop stimulating their hippocampus. Reduced fMRI activity and gray matter in the hippocampus were shown to correlate with cognitive deficits in normal aging. Therefore, these results have important implications regarding factors involved in healthy and successful aging.