Browsing by Author "Martin, Lindi"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Anxiety : an overlooked confounder in the characterisation of chronic stress-related conditions?
    (Public Library of Science, 2020-04-16) Viljoen, Monet; Benecke, Rohan M.; Martin, Lindi; Adams, Rozanne C. M.; Seedat, Soraya; Smith, Carine
    Although anxiety disorders are among the most prevalent of psychiatric disorders, childhood trauma-related studies seldom consider anxiety proneness as distinct aetiological contributor. We aimed to distinguish between trauma- and anxiety-associated physiological profiles. South African adolescent volunteers were categorised for trauma exposure (CTQ, mean score 39±11) and anxiety proneness (AP)(CASI, mean score 37±7, STAI-T, mean score 41±8). Circulating hormone and leukocyte glucocorticoid receptor levels, as well as leukocyte functional capacity, were assessed. AP was associated with lower DHEAs (P<0.05) and higher leukocyte GR expression (P<0.05). DHEAs was also negatively correlated with anxiety sensitivity (CASI, P<0.05). In conclusion, AP may have more predictive power than trauma in terms of health profile. Increased glucocorticoid sensitivity previously reported after trauma, may be a unique function of anxiety and not trauma exposure per se. DHEAs concentration was identified as potentially useful marker for monitoring progressive changes in HPA-axis sensitivity and correlated with psychological measures of anxiety.
  • Thumbnail Image
    Item
    Anxiety sensitivity in school attending youth : exploratory and confirmatory factor analysis of the 18-item CASI in a multicultural South African sample
    (Frontiers, 2016-01-07) Martin, Lindi; Kidd, Martin; Seedat, Soraya
    ENGLISH SUMMARY : Anxiety sensitivity (AS) is a risk factor for the development of anxiety disorders in youth. To date, the applicability of the Childhood Anxiety Sensitivity Index (CASI) in youth from a low or middle income country (LMIC) setting on the African continent has not been assessed. A representative sample of 1149 secondary school learners from 29 schools in Cape Town, South Africa, participated in the study. Participants completed the CASI on a single occasion. One-, two-, and four-factor models of the CASI were assessed. A one-factor solution that comprised items predominantly represented by physical concerns appeared to provide the best fit to our data, however, relatively low variance (26%) was explained. Subsequent item deletion resulted in a 9-item ‘physical concerns’ factor that showed good construct reliability (0.83) but also explained a low amount of variance (35%). In terms of gender, a one-factor model provided the best fit, however, low variance was explained (i.e., 25%). Configural, metric and scalar invariance of the CASI by gender was determined. Our results suggest that the 18-item CASI is not applicable to our target population and may require adaptation in this population; however, replication of this study in other multicultural adolescent samples in South Africa is first needed to further assess the validity of the AS construct as measured by the CASI.
  • Thumbnail Image
    Item
    Examining the influence of childhood trauma and epigenetic variation in brain-derived neurotrophic factor on anxiety sensitivity
    (Stellenbosch : Stellenbosch University, 2022-02) Chifamba, Leah; Martin, Lindi; Seedat, Soraya; Hemmings, Sian; Womersley, Jacqueline; Womersley, Jacqueline; Hemmings, Sian; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.
    ENGLISH ABSTRACT: Anxiety sensitivity (AS) is defined as the likelihood of interpreting anxiety-related bodily sensations as having potentially harmful effects on psychological and physical wellbeing. Anxiety sensitivity is a risk factor for the development of anxiety disorders. The aetiology of AS is linked to genetic and environmental interactions. One environmental factor that has been linked to AS is childhood trauma (CT). The gene encoding the brain-derived neurotrophic factor (BDNF) has been implicated in psychiatric disorders, as well as neuroplastic changes that can occur after CT exposure. These changes can occur via epigenetic mechanisms, chemical modifications of DNA that alter expression without altering DNA sequence. DNA methylation is one epigenetic mechanism. The aim was to determine the associative and interactive effects of CT and epigenetic variation in BDNF on AS in adolescents from South Africa. This study investigated BDNF single nucleotide polymorphisms (SNPs), and DNA methylation associated with AS and CT effects in 951 participants who self-identified as being Xhosa or South African Coloured (SAC). Six BDNF SNPs, rs11030099, rs6265, rs11030101, rs2049046, rs908867 and rs1491850 were genotyped in 951 participants. Methylation of BDNF promoter I CpG sites was assessed in a subset of participants (n = 90). Statistical analysis was performed using R programming. In Xhosa females, the rs11030101 TT genotype was associated with decreased AS (p = 0.032). Furthermore, rs2049046 AT genotype was associated with decreased AS (p = 0.009) in SAC females. The interaction of CT with the BDNF rs2049046 AA genotype was associated with lower AS (p = 0.029) in Xhosa females. No significant association was found between CT, AS and methylation, also no significant genetype interaction with CT on methylation was identified. Our results provide insight into the role of genetic variation in BDNF on AS in adolescents and emphasises the importance of examining the influence of gene x environment interactions on AS in differentiated ethnic and sex groups.
  • Thumbnail Image
    Item
    No gene-by-environment interaction of BDNF Val66Met polymorphism and childhood maltreatment on anxiety sensitivity in a mixed race adolescent sample
    (Taylor & Francis Open, 2018) Martin, Lindi; Hemmings, Sian M. J.; Kidd, Martin; Seedat, Soraya
    Background: Anxiety disorders in youth are attributable to multiple causal mechanisms, comprising biological vulnerabilities, such as genetics and temperament, and unfavourable environmental influences, such as childhood maltreatment (CM). Objective: A gene-environment (G x E) interaction study was conducted to determine the interactive effect of the BDNF Val66Met polymorphism and CM to increase susceptibility to anxiety sensitivity (AS) in a sample of mixed race adolescents. Method: Participants (n = 308, mean age = 15.8 years) who were all secondary school students and who completed measures for AS and CM were genotyped for the BDNF Val66Met polymorphism. Hierarchical multiple regression analysis was conducted to assess G x E influences on AS. Age and gender were included in the models as covariates as age was significantly associated with AS total score (p < .05), and females had significantly higher AS scores than males (p < .05). Results: A main effect of CM on AS was evident (p < .05), however, no main effect of BDNF genotype on AS was observed (p> .05). A non-significant G x E effect on AS was revealed (p <.05). Conclusions: Our results suggest that CM does not have a moderating role in the relationship between the BDNF Val66Met genotype and the increased risk of anxiety-related phenotypes, such as AS. Given the exploratory nature of this study, findings require replication in larger samples and adjustment for population stratification to further explore the role of BDNF Val66Met and CM on AS in mixed race adolescents.
  • Thumbnail Image
    Item
    Reported rapes at a hospital rape centre : demographic and clinical profiles
    (Health and Medical Publishing Group (HMPG), 2010) Lammers, Kees; Martin, Lindi; Andrews, Donovan; Seedat, Soraya