Table 1 Criteria that were used in rating the methodological quality of relevant studies.

External validity

Eligibility criteria were specified.

Internal and statistical validity

Subjects were randomly allocated to groups.

Allocation was concealed.

The groups were similar at baseline regarding the most important prognostic indicators.

There was blinding of all subjects.

There was blinding of all therapists who administered the therapy.

There was blinding of all assessors who measured at least one key outcome.

Measurements of at least one key outcome were obtained from more than 85% of the subjects initially allocated to groups.

All subjects for whom outcome measurements were available received the treatment or control condition as allocated, or where this was not the case, data for at least one key outcome were analyzed by "intention to treat".

The results of between-group statistical comparisons are reported for at least one key outcome.

The study provides both point measurements and measurements of variability for at least one key outcome.

Additional criterion external validity:

The staff, places and facilities where the patients were treated, were representative of the staff, places and facilities where the majority of the patients are intended to receive the treatment.