4 results
Job strain as a risk factor for clinical depression: systematic review and meta-analysis with additional individual participant data
- I. E. H. Madsen, S. T. Nyberg, L. L. Magnusson Hanson, J. E. Ferrie, K. Ahola, L. Alfredsson, G. D. Batty, J. B. Bjorner, M. Borritz, H. Burr, J.-F. Chastang, R. de Graaf, N. Dragano, M. Hamer, M. Jokela, A. Knutsson, M. Koskenvuo, A. Koskinen, C. Leineweber, I. Niedhammer, M. L. Nielsen, M. Nordin, T. Oksanen, J. H. Pejtersen, J. Pentti, I. Plaisier, P. Salo, A. Singh-Manoux, S. Suominen, M. ten Have, T. Theorell, S. Toppinen-Tanner, J. Vahtera, A. Väänänen, P. J. M. Westerholm, H. Westerlund, E. I. Fransson, K. Heikkilä, M. Virtanen, R. Rugulies, M. Kivimäki, for the IPD-Work Consortium
-
- Journal:
- Psychological Medicine / Volume 47 / Issue 8 / June 2017
- Published online by Cambridge University Press:
- 26 January 2017, pp. 1342-1356
-
- Article
-
- You have access Access
- Open access
- HTML
- Export citation
-
Background
Adverse psychosocial working environments characterized by job strain (the combination of high demands and low control at work) are associated with an increased risk of depressive symptoms among employees, but evidence on clinically diagnosed depression is scarce. We examined job strain as a risk factor for clinical depression.
MethodWe identified published cohort studies from a systematic literature search in PubMed and PsycNET and obtained 14 cohort studies with unpublished individual-level data from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium. Summary estimates of the association were obtained using random-effects models. Individual-level data analyses were based on a pre-published study protocol.
ResultsWe included six published studies with a total of 27 461 individuals and 914 incident cases of clinical depression. From unpublished datasets we included 120 221 individuals and 982 first episodes of hospital-treated clinical depression. Job strain was associated with an increased risk of clinical depression in both published [relative risk (RR) = 1.77, 95% confidence interval (CI) 1.47–2.13] and unpublished datasets (RR = 1.27, 95% CI 1.04–1.55). Further individual participant analyses showed a similar association across sociodemographic subgroups and after excluding individuals with baseline somatic disease. The association was unchanged when excluding individuals with baseline depressive symptoms (RR = 1.25, 95% CI 0.94–1.65), but attenuated on adjustment for a continuous depressive symptoms score (RR = 1.03, 95% CI 0.81–1.32).
ConclusionsJob strain may precipitate clinical depression among employees. Future intervention studies should test whether job strain is a modifiable risk factor for depression.
Spectral content of cloud cavitation about a sphere
- K. L. de Graaf, P. A. Brandner, B. W. Pearce
-
- Journal:
- Journal of Fluid Mechanics / Volume 812 / 10 February 2017
- Published online by Cambridge University Press:
- 22 December 2016, R1
-
- Article
- Export citation
-
The physics and spectral content of cloud cavitation about a sphere are investigated in a variable-pressure water tunnel using dynamic surface pressure measurement and high-speed imaging. Experiments are conducted using a polyvinyl chloride sphere at a Reynolds number of $1.5\times 10^{6}$ with cavitation numbers, $\unicode[STIX]{x1D70E}$, ranging from inception to supercavitation. Three distinct shedding regimes are identified: a uni-modal regime for $\unicode[STIX]{x1D70E}>0.9$ and two bi-modal regimes for $0.9>\unicode[STIX]{x1D70E}>0.675$ and $0.675>\unicode[STIX]{x1D70E}>0.3$. For small cavity lengths ($\unicode[STIX]{x1D70E}>0.9$), Kelvin–Helmholtz instability and transition to turbulence in the overlying separated boundary layer form the basis for cavity breakup and coherent vortex formation. At greater lengths ($\unicode[STIX]{x1D70E}<0.9$), larger-scale shedding ensues, driven by coupled re-entrant jet formation and shockwave propagation. Strong adverse pressure gradients about the sphere lead to accumulation and radial growth of re-entrant flow, initiating breakup, from which, in every case, a condensation shockwave propagates upstream causing cavity collapse. When the shedding is most energetic, shockwave propagation upstream may cause large-scale leading edge extinction. The bi-modal response is due to cavity shedding being either axisymmetric or asymmetric. The two bi-modal regimes correspond to $\unicode[STIX]{x1D70E}$ ranges where the cavity and re-entrant jet either remain attached or become detached from the sphere. There is a distinct frequency offset at transition between regimes in both shedding modes. Despite the greater cavity lengths at lower $\unicode[STIX]{x1D70E}$ values, the second bi-modal regime initially exhibits shorter shedding periods due to increased cavity growth rates. The second regime persists until supercavitation develops for $\unicode[STIX]{x1D70E}<0.3$.
Predictors of treatment dropout in self-guided web-based interventions for depression: an ‘individual patient data’ meta-analysis
- E. Karyotaki, A. Kleiboer, F. Smit, D. T. Turner, A. M. Pastor, G. Andersson, T. Berger, C. Botella, J. M. Breton, P. Carlbring, H. Christensen, E. de Graaf, K. Griffiths, T. Donker, L. Farrer, M. J. H. Huibers, J. Lenndin, A. Mackinnon, B. Meyer, S. Moritz, H. Riper, V. Spek, K. Vernmark, P. Cuijpers
-
- Journal:
- Psychological Medicine / Volume 45 / Issue 13 / October 2015
- Published online by Cambridge University Press:
- 17 April 2015, pp. 2717-2726
-
- Article
- Export citation
-
Background
It is well known that web-based interventions can be effective treatments for depression. However, dropout rates in web-based interventions are typically high, especially in self-guided web-based interventions. Rigorous empirical evidence regarding factors influencing dropout in self-guided web-based interventions is lacking due to small study sample sizes. In this paper we examined predictors of dropout in an individual patient data meta-analysis to gain a better understanding of who may benefit from these interventions.
MethodA comprehensive literature search for all randomized controlled trials (RCTs) of psychotherapy for adults with depression from 2006 to January 2013 was conducted. Next, we approached authors to collect the primary data of the selected studies. Predictors of dropout, such as socio-demographic, clinical, and intervention characteristics were examined.
ResultsData from 2705 participants across ten RCTs of self-guided web-based interventions for depression were analysed. The multivariate analysis indicated that male gender [relative risk (RR) 1.08], lower educational level (primary education, RR 1.26) and co-morbid anxiety symptoms (RR 1.18) significantly increased the risk of dropping out, while for every additional 4 years of age, the risk of dropping out significantly decreased (RR 0.94).
ConclusionsDropout can be predicted by several variables and is not randomly distributed. This knowledge may inform tailoring of online self-help interventions to prevent dropout in identified groups at risk.
Cavitation about a jet in crossflow
- P. A. Brandner, B. W. Pearce, K. L. de Graaf
-
- Journal:
- Journal of Fluid Mechanics / Volume 768 / 10 April 2015
- Published online by Cambridge University Press:
- 04 March 2015, pp. 141-174
-
- Article
- Export citation
-
Cavitation occurrence about a jet in crossflow is investigated experimentally in a variable-pressure water tunnel using still and high-speed photography. The 0.012 m diameter jet is injected on the centreplane of a 0.6 m square test section at jet to freestream velocity ratios ranging from 0.2 to 1.6, corresponding to jet-velocity-based Reynolds numbers of $25\times 10^{3}$ to $160\times 10^{3}$ respectively. Measurements were made at a fixed freestream-based Reynolds number, for which the ratio of the undisturbed boundary layer thickness to jet diameter is 1.18. The cavitation number was varied from inception (up to about 10) down to 0.1. Inception is investigated acoustically for bounding cases of high and low susceptibility to phase change. The influence of velocity ratio and cavitation number on cavity topology and geometry are quantified from the photography. High-speed photographic recordings made at 6 kHz provide insight into cavity dynamics, and derived time series of spatially averaged pixel intensities enable frequency analysis of coherent phenomena. Cavitation inception was found to occur in the high-shear regions either side of the exiting jet and to be of an intermittent nature, increasing in occurrence and duration from 0 to 100 % probability with decreasing cavitation number or increasing jet to freestream velocity ratio. The frequency and duration of individual events strongly depends on the cavitation nuclei supply within the approaching boundary layer. Macroscopic cavitation develops downstream of the jet with reduction of the cavitation number beyond inception, the length of which has a power-law dependence on the cavitation number and a linear dependence on the jet to freestream velocity ratio. The cavity closure develops a re-entrant jet with increase in length forming a standing wave within the cavity. For sufficiently low cavitation numbers the projection of the re-entrant jet fluid no longer reaches the cavity leading edge, analogous to supercavitation forming about solid cavitators. Hairpin-shaped vortices are coherently shed from the cavity closure via mechanisms of shear-layer roll-up similar to those shed from protuberances and jets in crossflow in single-phase flows. These vortices are shed at an apparently constant frequency, independent of the jet to freestream velocity ratio but decreasing in frequency with reducing cavitation number and cavity volume growth. Highly coherent cavitating vortices form along the leading part of the cavity due to instability of the jet upstream shear layer for jet to freestream velocity ratios greater than about 0.8. These vortices are cancelled and condense as they approach the trailing edge in the shear layer of opposing vorticity associated with the cavity closure and the hairpin vortex formation. For lower velocity ratios, where there is decreased jet penetration, the jet upstream shear velocity gradient reverses and vortices of the opposite sense form, randomly modulated by boundary layer turbulence.