Table 1

Studies within mental healthcare that investigated the rate and severity or potential severity of medication errors

Date and setting	Study design and data source	Error type studied	Number of errors	Rate of errors	Severity or potential severity of harm caused by errors
NHS, National Health Service.
1991–1997; England, NHS mental health inpatient units for older people⁸	Retrospective process based; all prescription charts for index admission of 112 patients	Prescribing (psychotropics only)	92 patient prescription records contained an error	0.82 per patient episode	No information given

2000; Japan, 85 long-stay wards in 44 private psychiatric hospitals¹⁴	Prospective process based; clinician reports on incident reporting system over 2 months	Administration, dispensing and prescribing	221 reports	0.79 per 1000 patient days	56.6% insignificant, 14.9% potentially significant, 28.5% potentially serious

2000–2004; England, tertiary private psychiatric hospital¹⁵	Prospective process based; all administration errors reported over 42 months on incident reporting system	Administration	112 reports	2.67 per month	77% no or minimal significance, 14% moderate significance, 1% potentially serious, 0% potentially fatal
2001; USA, 103-bedded state psychiatric hospital⁹	Mixed process-based involving random sample of 31 of 95 patients discharged over a 5-month period	Administration, dispensing, prescribing and transcription	2194 potential incidents v 9 clinician reports; ratio 244:1 (p<0.001)	1516 potential incidents v 6.22 clinician reports per 1000 patient days	19% were low risk, 23% moderate risk and 58% high risk
	• Retrospective potential incidents—chart review of entire hospitalisation and prospective reporting of dispensing errors for equivalent number of patient days.
	• Prospective clinician reports on incident reporting system.

2002; England, tertiary private psychiatric hospital¹⁰	Prospective process based; inpatient errors detected by pharmacists in course of routine work over 1 month	Prescribing	311 reports	0.022 per prescribed item	56% insignificant, 36% minimal, 27% definitely significant, 0% potentially fatal

2002; England, 12 NHS mental health trusts¹¹	Prospective process based; pharmacists completed intervention forms over 1 month	Prescribing	557 reports	No denominator given with which to calculate a rate of error	11% of errors had a “potentially serious outcome”

2003; England, tertiary private psychiatric hospital¹²	Prospective process based; errors detected by pharmacists in course of routine work over 1 month	Prescribing	211 reports	No denominator given with which to calculate a rate of error	64.5% insignificant, 24.2% minimal, 11.4% definitely significant, 0% potentially fatal

2004; England, single NHS mental health trust⁶	Prospective process based; clinician reports on a new medication error reporting system over 12 months.	Administration, dispensing and prescribing	66 reports	5.5 per month	40 low severity, 23 moderate, 3 high

2004; England and Wales, 9 centres (8 NHS and 1 independent sector) providing mental health services¹³	Prospective process based; errors detected by pharmacists during course of routine work over 5 days	Prescribing	523 reports	0.024 per prescribed item	47.8% negligible, 45.9% minor, 3.3% serious, 1% potentially fatal