Depression anxiety stress scales-21 : Factor structure and test-retest invariance, and temporal stability and uniqueness of latent factors in older adults
- Authors: Gomez, Rapson , Summers, Mathew , Summers, Avril , Wolf, Anna , Summers, Jeff
- Date: 2014
- Type: Text , Journal article
- Relation: Journal of Psychopathology and Behavioral Assessment Vol. 36, no. 2 (2014), p. 308-317
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- Description: This study examined the factor structure and test-retest invariance, and temporal stability and uniqueness of the latent factors (depression, anxiety, and stress) of the Depression Anxiety Stress Scales-21 (DASS-21; Lovibond & Lovibond, 1995) in group a of 269 older adults (age ranging from 60 to 85 years) from the general community. Participants completed the DASS-21 twice, 3 months apart. Confirmatory factor analysis (CFA) of their ratings at Time 1 indicated support for the original 3-factor oblique model (factors for depression, anxiety, and stress). Additional analyses showed support for test-retest invariance for both the measurement (configural, metric and thresholds) and structural (variances and covariances) components of this model. Results also indicated temporal stability and uniqueness of the latent factors. The practical, theoretical, research and clinical implications of the findings are discussed. © 2013 Springer Science+Business Media.
Depression anxiety stress scales-21 : Measurement and structural invariance across ratings of men and women
- Authors: Gomez, Rapson , Summers, Mathew , Summers, Avril , Wolf, Anna , Summers, Jeff
- Date: 2014
- Type: Text , Journal article
- Relation: Assessment Vol. 21, no. 4 (2014), p. 418-426
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- Description: The current study examined the measurement and structural invariance of the Depression Anxiety Stress Scales-21 (DASS-21) across ratings provided by men (N = 227) and women (N = 460). Multiple-group confirmatory factor analysis (CFA) supported full metric invariance and intercepts invariance for 20 of the 21 items. Invariance for all item intercepts was supported by multiple indicators multiple causes (MIMIC) procedure that controlled for the effects of age. Multiple-group CFA supported invariance for all factor variances and covariances. This procedure and the MIMIC analyses found equivalency for all latent mean scores. These findings indicate good support for measurement and structural invariance of the DASS-21 rating across men and women. The psychometric and practical implications of the findings are discussed.
Duration-dependent effects of the BDNF Val66Met polymorphism on anodal tDCS induced motor cortex plasticity in older adults : A group and individual perspective
- Authors: Puri, Rohan , Hinder, Mark , Fujiyama, Hakuei , Gomez, Rapson , Carson, Richard , Summers, Jeff
- Date: 2015
- Type: Text , Journal article
- Relation: Frontiers in Aging Neuroscience Vol. 7, no. JUN (2015), p. 1-10
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- Description: The brain derived neurotrophic factor (BDNF) Val66Met polymorphism and stimulation duration are thought to play an important role in modulating motor cortex plasticity induced by non-invasive brain stimulation (NBS). In the present study we sought to determine whether these factors interact or exert independent effects in older adults. Fifty-four healthy older adults (mean age = 66.85 years) underwent two counterbalanced sessions of 1.5 mA anodal transcranial direct current stimulation (atDCS), applied over left M1 for either 10 or 20 min. Single pulse transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability (CSE) before and every 5 min for 30 min following atDCS. On a group level, there was an interaction between stimulation duration and BDNF genotype, with Met carriers (n = 13) showing greater post-intervention potentiation of CSE compared to Val66Val homozygotes homozygotes (n = 37) following 20 min (p = 0.002) but not 10 min (p = 0.219) of stimulation. Moreover, Met carriers, but not Val/Val homozygotes, exhibited larger responses to TMS (p = 0.046) after 20 min atDCS, than following 10 min atDCS. On an individual level, two-step cluster analysis revealed a considerable degree of inter-individual variability, with under half of the total sample (42%) showing the expected potentiation of CSE in response to atDCS across both sessions. Intra-individual variability in response to different durations of atDCS was also apparent, with one-third of the total sample (34%) exhibiting LTP-like effects in one session but LTD-like effects in the other session. Both the inter-individual (p = 0.027) and intra-individual (p = 0.04) variability was associated with BDNF genotype. In older adults, the BDNF Val66Met polymorphism along with stimulation duration appears to play a role in modulating tDCS-induced motor cortex plasticity. The results may have implications for the design of NBS protocols for healthy and diseased aged populations. © 2015 Puri, Hinder, Fujiyama, Gomez, Carson and Summers.