Table 1.

World Mental Health (WMH) sample characteristics by World Bank income categories^a, and sample for psychotic experiences (PEs) after exclusion of 140 respondents who were screen-positive for possible schizophrenia/psychosis^b

Country by income categorya	Sample characteristicsc, d	Field dates	Age range	Sample size		Response ratee
				Part I	PEs sample
I. Low and lower middle income countries
Colombia	All urban areas of the country	2003	18–65	4,426	722	87.7
Iraq	Nationally representative	2006–7	18–96	4,332	4,329	95.2
Nigeria	21 of the 36 states in the country	2002–3	18–100	6,752	1,417	79.3
PRCf – Shenzheng	Shenzhen metropolitan area	2006–7	18–88	7,132	2,468	80.0
Peru	Nationally representative	2004–5	18–65	3,930	530	90.2
TOTAL				26,572	9,466	84.7
II. Upper-middle income countries
Brazil - São Paulo	São Paulo metropolitan area	2005–7	18–93	5,037	2,922	81.3
Lebanon	Nationally representative	2002–3	18–94	2,857	1,029	70.0
Mexico	All urban areas of the country	2001–2	18–65	5,782	715	76.6
Romania	Nationally representative	2005–6	18–96	2,357	2,357	70.9
TOTAL				16,033	7,023	75.8
III. High-income countries
Belgium	Nationally representative	2001–2	18–95	2,419	319	50.6
France	Nationally representative	2001–2	18–97	2,894	301	45.9
Germany	Nationally representative	2002–3	18–95	3,555	408	57.8
Italy	Nationally representative	2001–2	18–100	4,712	617	71.3
Netherlands	Nationally representative	2002–3	18–95	2,372	348	56.4
New Zealandg	Nationally representative	2003–4	18–98	12,790	7,263	73.3
Portugal	Nationally representative	2008–9	18–81	3,849	2,053	57.3
Spain	Nationally representative	2001–2	18–98	5,473	1,159	78.6
United States	Nationally representative	2002–3	18–99	9,282	2,304	70.9
TOTAL				47,346	14,772	65.5
IV. Total				89,951	31,261	72.1

^aBased on World Bank country level of economic development (The World Bank. (2008). Data and Statistics. Accessed May 12, 2009 at: http://go.worldbank.org/D7SN0B8YU0)

^bRespondents were excluded if they endorsed any PE but also (a) reported (1) schizophrenia/psychosis or (2) manic-depression/mania” in response to the question “What did the doctor say was causing (this/these) experiences?”; and (b) those who ever took any antipsychotic medications for these symptoms. This resulted in the exclusion of 140 respondents (0.4% of all respondents), leaving 31,261 respondents for this study.

^cNSMH (The Colombian National Study of Mental Health); IMHS (Iraq Mental Health Survey); NSMHW (The Nigerian Survey of Mental Health and Wellbeing); EMSMP (La Encuesta Mundial de Salud Mental en el Peru); LEBANON (Lebanese Evaluation of the Burden of Ailments and Needs of the Nation); M-NCS (The Mexico National Comorbidity Survey); RMHS (Romania Mental Health Survey); ESEMeD (The European Study Of The Epidemiology Of Mental Disorders); NZMHS (New Zealand Mental Health Survey); NMHS (Portugal National Mental Health Survey); NCS-R (The US National Comorbidity Survey Replication).

^dMost WMH surveys are based on stratified multistage clustered area probability household samples in which samples of areas equivalent to counties or municipalities in the US were selected in the first stage followed by one or more subsequent stages of geographic sampling (e.g., towns within counties, blocks within towns, households within blocks) to arrive at a sample of households, in each of which a listing of household members was created and one or two people were selected from this listing to be interviewed. No substitution was allowed when the originally sampled household resident could not be interviewed. These household samples were selected from Census area data in all countries other than France (where telephone directories were used to select households) and the Netherlands (where postal registries were used to select households). Several WMH surveys (Belgium, Germany, and Italy) used municipal resident registries to select respondents without listing households. 13 of the 18 surveys are based on nationally representative household samples.

^eThe response rate is calculated as the ratio of the number of households in which an interview was completed to the number of households originally sampled, excluding from the denominator households known not to be eligible either because of being vacant at the time of initial contact or because the residents were unable to speak the designated languages of the survey. The weighted average response rate is 72.1%.

^fPeople’s Republic of China

^gFor the purposes of cross-national comparisons we limit the sample to those 18+.