1993-lipsey.pdf: “The Efficacy of Psychological, Educational, and Behavioral Treatment: Confirmation from Meta-Analysis”, (1993-12-01; ):
Conventional reviews of research on the efficacy of psychological, educational, and behavioral treatments often find considerable variation in outcome among studies and, as a consequence, fail to reach firm conclusions about the overall effectiveness of the interventions in question. In contrast, meta-analysis reviews show a strong, dramatic pattern of positive overall effects that cannot readily be explained as artifacts of meta-analytic technique or generalized placebo effects. Moreover, the effects are not so small that they can be dismissed as lacking practical or clinical-significance. Although has limitations, there are good reasons to believe that its results are more credible than those of conventional reviews and to conclude that well-developed psychological, educational, and behavioral treatment is generally efficacious.
“Meta-Regression Analyses, Meta-Analyses, and Trial Sequential Analyses of the Effects of Supplementation with Beta-Carotene, Vitamin A, and Vitamin E Singly or in Different Combinations on All-Cause Mortality: Do We Have Evidence for Lack of Harm?”, (2013-08-04):
Background and Aims: Evidence shows that antioxidant supplements may increase mortality. Our aims were to assess whether different doses of beta-carotene, vitamin A, and vitamin E affect mortality in primary and secondary prevention randomized clinical trials with low risk of bias.
Methods: The present study is based on our 2012 Cochrane systematic review analyzing beneficial and harmful effects of antioxidant supplements in adults. Using random-effects meta-analyses, meta-regression analyses, and trial sequential analyses, we examined the association between beta-carotene, vitamin A, and vitamin E, and mortality according to their daily doses and doses below and above the recommended daily allowances (RDA).
Results: We included 53 randomized trials with low risk of bias (241,883 participants, aged 18 to 103 years, 44.6% women) assessing beta-carotene, vitamin A, and vitamin E. Meta-regression analysis showed that the dose of vitamin A was statistically-significantly positively associated with all-cause mortality. Beta-carotene in a dose above 9.6 mg statistically-significantly increased mortality (relative risk (RR) 1.06, 95% confidence interval (CI) 1.02 to 1.09, I2 = 13%). Vitamin A in a dose above the RDA (> 800 µg) did not statistically-significantly influence mortality (RR 1.08, 95% CI 0.98 to 1.19, I2 = 53%). Vitamin E in a dose above the RDA (> 15 mg) statistically-significantly increased mortality (RR 1.03, 95% 1.00 to 1.05, I2 = 0%). Doses below the RDAs did not affect mortality, but data were sparse.
Conclusions: Beta-carotene and vitamin E in doses higher than the RDA seem to statistically-significantly increase mortality, whereas we lack information on vitamin A. Dose of vitamin A was statistically-significantly associated with increased mortality in meta-regression. We lack information on doses below the RDA.
Background: All essential compounds to stay healthy cannot be synthesized in our body. Therefore, these compounds must be taken through our diet or obtained in other ways. Oxidative stress has been suggested to cause a variety of diseases. Therefore, it is speculated that antioxidant supplements could have a potential role in preventing diseases and death. Despite the fact that a normal diet in high-income countries may provide sufficient amounts of antioxidants, more than one third of adults regularly take antioxidant supplements.