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Table 1 Characteristics of the included studies

From: Serum folate levels in bipolar disorder: a systematic review and meta-analysis

Author (year)

Study design

Criteria

bipolar subtype

symptom severity

Mood state and subjects’ characteristics

n (male/female)

Mean age

Source and assay

Comorbidities and exclusion criteria

Doganavsargil Baysal, G.O. (2013)

case-control study

DSM-IV-TR

bipolar I disorder

maintain

Euthymic patient

Healthy control

60 (n/a)

20 (n/a)

n/a

Serum, n/a

Patients who had neurologic diseases, cardiovascular diseases, renal diseases, diabetes mellitus, hypo/hyperthyroid- ism, non-psychotropic drug use that could affect HCY levels, substance abuse, an IQ score below 80 based on the WAIS-R test (Epir and Iskit, 1972), a history of electroconvulsive therapy during the previous 6 months, or patients who tested positive for biochemical markers suggestive of abnormal thyroid, liver or renal functions were not included in the study.

Ezzaher, A. (2011)

case-control study

DSM-IV

bipolar I disorder

n/a

Depressive, manic, euthymic patient

Healthy control

92 (62/30)

170 (79/91)

36.0 ± 11.1

43.7 ± 14.2

Serum, microparticle enzyme immunoassay on Elecsys 2010

The exclusion criteria were age < 18 years, other psychiatric illnesses, epilepsy, mental retardation, hormone therapy, history of vitamin use, diabetes, cardiovascular disease, thyroid dysfunction, liver disease, or renal dysfunction.

Diass, V.V. (2009)

case-control study

DSM-IV

bipolar I disorder

maintain

Euthymic patient

Healthy control

65 (24/41)

49 (14/35)

37.8 ± 10.5

33.6 ± 9.8

Serum, electrochemiluminescence immunoassay

Patients with neurological disorders, previous head trauma, physical illnesses requiring medical intervention, substance abuse, or an ECT course in the preceding 6 months were excluded.

Ozbek, Z. (2008)

case-control study

DSM-IV

Bipolar disorder

n/a

Unspecified mood patient

Healthy control

197 (74/123)

238 (67/171)

40.6 ± 12.2

41.3 ± 12.7

Serum, electrochemiluminescence immunoassay

None of the subjects had significant neurological comorbidity, epilepsy, mental retardation or a history of substance abuse.

None of the subjects presented with current or past history of cardiovascular disease, endocrinological and metabolic disease, or a family history of coronary heart disease.

Lerner, V. (2006)

case-control study

DSM-IV

bipolar I disorder

acute

Mania, inpatient

Healthy control

22 (n/a)

250 (156/94)

n/a

42.17 ± 14.2

Serum, Electrochemiluminescence

n/a

Hasanah, C.I. (1997)

case-control study

DSM-III-R

bipolar I disorder

acute

Mania, inpatient

Healthy control

45 (24/21)

33 (13/20)

30.0

29.0

serum, the IMx system

The exclusion criteria were, mood incongruent psychotic features, concomitant medical illness, substance misuse, pregnancy, puerperium and those on drug treatment. Those with noticeable weight loss by close relatives were also excluded.

  1. Abbreviation: DSM-IV-TR Diagnostic and Statistical Manual of Mental Disorders, 4th edition, Text-Revision; DSM-IV Diagnostic and Statistical Manual of Mental Disorders, 4th edition; DSM-III-R Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, Revision; n/a not available