Sixteen RCTs with 554 participants randomised were included in the review. The mean number of participants in the studies was 35.
Two studies compared EMDR with a control group.
Four studies compared EMDR with a delayed treatment group.
Six studies compared EMDR with other forms of psychotherapy: cognitive behavioural therapy; cognitive psychodynamic behavioural psychotherapy, antidepressants, group relaxation training, panic and anxiety reduction; biofeedback assisted relaxation; image habituation training and applied muscle relaxation; active listening; and exposure therapy.
Six studies compared standard EMDR with the following variants: time interval condition with eyes fixed; finger tapping instead of eye movements; automated EMDR with flashing lights; eyes fixed condition; eyes concentrating on a stationary flashing light; EMDR followed by same procedure with eyes fixed (crossover design); same procedure without cognitive reprocessing; same procedure with eyes fixed; and control group.
The studies were of variable methodological quality. Only 4 studies providing details of randomisation and only 5 reported the blinding of outcome assessors to treatment allocation, in some cases with high loss to follow-up.
All but one trial detected a statistically-significant positive treatment effect for EMDR. The size of the treatment effect varied between 0.17 and 1.67. In the majority of cases, the effect size was larger for EMDR than for the comparators; in 4 cases it was twice as large.
In most cases, EMDR was shown to be effective at reducing symptoms up to 3 months after treatment. In one case, benefit was maintained up to 9 months and in another (uncontrolled), the treatment effect was still present at 15 months. Two studies suggested that EMDR was as effective as exposure therapies, 3 studies claimed greater effectiveness in comparison to relaxation training, and 3 studies claim superiority over delayed treatment groups. Of the studies examining specific treatment components, 2 found that treatment with eyes moving was more effective than eyes fixed, while 3 studies found the two procedures to be of equal effectiveness.