Sub-analyses revealed that self-help interventions had a small-to-medium-sized effect on positive symptoms (d+ = 0.42, 95% CI: 0.13 to 0.72), a small-to-medium-sized effect on negative symptoms (d+ = 0.37, 95% CI: 0.07 to 0.66), and a small-sized effect on outcomes associated with the symptoms of psychosis such as quality of life (d+ = 0.13, 95% CI: 0.02 to 0.24).
It is widely accepted that Cohen's d values of 0.2 – 0.49 denote small sized effects; 0.5 – 0.79 denote medium sized effects; and >0.8 denote large effect sizes.
Nicotine had a small- to medium-sized effect on subjective appetite and significantly altered food cue reactivity in a region sensitive to caloric intake that extended from the right hypothalamus to the basal ganglia.
Self-help interventions had, on average, a small-to-medium-sized effect on overall symptoms (d+ = 0.33, 95% CI: 0.17 to 0.48).
An intriguing finding of the study was the small sized placebo effect observed for patient reported outcomes.
However, considering the small sized placebo effect observed in this study, the results described should be viewed with caution.
The target sample size is 320 participants, which is based on power calculations required to identify small to medium sized effects for the primary study hypotheses.
In contrast, there were moderate-sized effects on overall FM impact and quality of life, small effects on depression and anxiety, and - of greatest concern - no effects on pain.
For example, a meta-analysis of self-control training on self-control task performance found a medium-sized effect [ 81] and a recent meta-analysis of response-inhibition training, using similar tasks to those used in the current study, on health behavior found a small-to-medium sized effect [ 94].
This might be due to the filling effect of the very small sized particles of LWFs.
The results from their review revealed that acute exercise had moderate-sized effects on short-term memory and moderate to large-sized effects on long-term memory [5].
