Table 3. Results of meta-regression analyses comparing prison suicide rate with general population suicide rate, incarceration rate, and other prison-level variables.

	Number of countries (n)*	Beta coefficient (b)	95% CI	p value
Annual suicide rate per 100 000 general population aged 30–49 years	20	–0·002	–3·886 to 3·88	0·99
Incarceration rate per 100 000 general population	20	–0·504	–0·895 to –0·114	0·014
Rate of overcrowding	20	0·987	–0·449 to 2·414	0·17
Ratio of prisoners to prison officers	18	–13·372	–32·645 to 5·900	0·16
Ratio of prisoners to health-care staff	11	0·010	–0·081 to 0·100	0·81
Ratio of prisoners to educational staff	11	–0·040	–0·240 to 0·160	0·66
Mean daily spend per prisoner	19	0·206	–0·033 to 0·444	0·086
Prison population turnover ratio	13	–0·167	–2·092 to 1·759	0·85
Management of prison health-care system†	10	39·898	–19·930 to 99·726	0·16
Mean forensic inpatient bed rate	5	1·783	–5·492 to 9·057	0·49
Mean length of imprisonment	16	–1·309	–4·633 to 2·015	0·41

^*Countries with five events of suicide or fewer (n=3) and the USA were excluded from these analyses.

^†Categorised as: 1=National Health Service; 2=Justice System.