Table 1. Characteristics of six randomized controlled trials included in the meta-analysis about adjunctive treatment of metformin for patients with schizophrenia being treated with clozapine
| study | diagnostic
criteria |
blind assessment
/control group |
sample
size (males, %) |
mean
age (years) |
mean duration
of illness (years) |
metformin
dosage (mg/day) |
duration of
follow-up (weeks) |
| N/A, no information available
CCMD-2, Chinese Classification of Mental Disorders, 2nd edition[12] CCMD-3, Chinese Classification of Mental Disorders, 3rd edition[13] DSM-IV, Diagnostic and Statistical Manual of the American Psychiatric Association, 4th edition[15] | |||||||
| Zhang 2004[28] | CCMD-2 | not blinded
no adjunctive treatment |
60
(45%) |
41 | N/A | 500 | 6 |
| Carrizo 2009[7] | DSM-IV | double-blind
placebo-controlled |
61
(N/A) |
38.8 | N/A | 1000 | 14 |
| Liu 2012[25] | CCMD-3 | not blinded
no adjunctive treatment |
100
(61%) |
N/A | 4.6 | 250-500 | 12 |
| Chen 2013[24] | DSM-IV | double-blind
placebo-controlled |
55
(51%) |
41.6 | N/A | 1500 | 24 |
| Wu 2014[27] | CCMD-3 | not blinded
no adjunctive treatment |
78
(59%) |
26.5 | 1.8 | 1000 | 12 |
| Hebrani 2015[26] | DSM-IV | double-blind
placebo-controlled |
60
(46%) |
46.5 | 20.2 | 1000 | 20 |