Skip to main content
Creating a new NHS England: NHS England and NHS Digital merged on 1 February 2023. More about the merger.

Publication, Part of

Statistics on Drug Misuse, England 2020

Official statistics, National statistics

National Statistics

Data quality statement


This document constitutes a background quality report for the Statistics on drugs misuse publication. 


This annual compendium report presents newly published information on hospital admissions attributable to drug related mental health and behavioural disorders and on hospital admissions attributable to poisoning by illicit drugs.

The report also provides links to information on drug misuse among both adults and children from a variety of sources, including previously published information from datasets and surveys such as the National Drug Treatment Monitoring System and the Crime Survey for England and Wales.

The report is published on the NHS Digital website at:

Statistics on Drug Misuse - NHS Digital

Purpose of document

This data quality statement aims to provide users with an evidence based assessment of quality of the statistical output included in this publication. 

It reports against those of the nine European Statistical System (ESS) quality dimensions and principles appropriate to this output. In doing so, this meets NHS Digital’s obligation to comply with the UK Statistics Authority (UKSA) Code of Practice for Statistics , and the following principles in particular:

  • Trustworthiness pillar, principle 6 (Data Governance) which states “Organisations should look after people’s information securely and manage data in ways that are consistent with relevant legislation and serve the public good.”
  • Quality pillar, principle 3 (Assured Quality) which states “Producers of statistics and data should explain clearly how they assure themselves that statistics and data are accurate, reliable, coherent and timely.”
  • Value pillar, principle 1 (Relevance to Users) which states “Users of statistics and data should be at the centre of statistical production; their needs should be understood, their views sought and acted upon, and their use of statistics supported.”
  • Value pillar, principle 2 (Accessibility) which states “Statistics and data should be equally available to all, not given to some people before others. They should be published at a sufficient level of detail and remain publicly available.”



This dimension covers the degree to which the statistical product meets user needs in both coverage and content.

This publication is considered to be of particular interest to central and local government, the NHS and independent sector providers in England and to English NHS commissioning organisations. However, data and findings are likely also to be of interest to a much broader base of users and are widely reported in the media.

Accuracy and reliability

This dimension covers the degree to which the statistical product meets user needs in both coverage and content.

This report is a National Statistic and is produced according to the Code of Practice for Official Statistics.

Most of the information in this report has been previously published. The sources of the information are trusted sources; the majority being either National or Official Statistics. Most sources referenced in this report include a Methodology section for further information.

Hospital admissions data

The data presented in this report are for inpatients only and therefore does not reflect all hospital activity. This should be considered when interpreting the data as recording and clinical practice may vary over time and between regions.

Some caution is necessary when looking at these data as, drug misuse may only be suspected and may not always be recorded by the hospital and, where drug misuse is recorded, it may not be possible to identify which drug(s) may be involved.

Further general information on HES data quality, including specific known issues can be found here:

The processing cycle and HES data quality - NHS Digital

COVID-19 and the production of statistics:  Due to the coronavirus illness (COVID-19) disruption, it would seem that there is some effect on the quality and coverage of some of our statistics in relation to the 2020/21 period. It is known that many hospitals are reporting zero or significantly less activity across one or more datasets for March 2020 onwards. The HES data in this publication relates to 2019/20, therefore, the end of the reporting period for this publication includes some of the pandemic period but this is estimated to have a negligible impact on the data.

Survey data

Some of the information signposted in the report is taken from survey data. Sometimes the mode of data collection used in a survey can have an impact on how respondents answer the questionnaire. For example, surveys conducted via a face-to-face interview such as the Crime Survey for England and Wales (CSEW) provide an opportunity for an interviewer to use a computer to record the respondent’s answers which will improve the quality of the data by ensuring all the questions are completed and not allowing any invalid or inconsistent answers. By comparison data collected via a self-completion survey such as Smoking, Drinking and Drug Use Amongst Young People (SDD) will have none of these inbuilt validations.

Face-to-face interviews also provide an opportunity to guide the respondent through any interpretation issues, which is more difficult in self-completion surveys.

Both modes however may suffer from respondents being tempted to give answers which are considered to be more socially acceptable. This could occur either through the surveys being completed in the home when other family members are present, or through the interviewer being present at a face-to-face interview. This effect is reduced in surveys such as Smoking, Drinking and Drugs (SDD) which is conducted in schools in exam conditions.

Timeliness and punctuality

Timeliness refers to the time gap between publication and the reference period. Punctuality refers to the gap between planned and actual publication dates.

This compendia report is published annually and presents or signposts the most up-to-date information available.

The publication of this report was delayed from July 2020 due to the coronavirus pandemic (COVID-19) requiring changes to NHS Digital’s statistical production schedule.

Accessibility and clarity

Accessibility is the ease with which users are able to access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the metadata, illustrations and accompanying advice.

The report is accessible on the NHS Digital website either in HTML format or as a PDF document. All tables in the report are provided in Excel format and as csv files, as part of the government’s requirement to make public data public.

The publication may be requested in large print or other formats through the NHS Digital contact centre: (please include ‘Statistics on Drug Misuse’ in the subject line).

Coherence and comparability

Coherence is the degree to which data which have been derived from different sources or methods, but refer to the same topic, are similar. Comparability is the degree to which data can be compared over time and domain.

Hospital admissions where drug-related mental and behavioural disorders were a factor

There is continuing evidence that recording of secondary diagnosis codes is improving over time, which may have contributed (though not fully) to the increases seen over the last ten years for this measure. This is demonstrated by looking at year on year increases in the mean number of secondary diagnosis codes that were applied to these admissions, as shown below.

Year of Admission Mean number of diagnosis codes Percent (%) difference from previous year
2007/08 3.3 N/A
2008/09 3.5 8.6
2009/10 3.8 6.6
2010/11 4.3 13.7
2011/12 4.4 3.4
2012/13 4.6 4.3
2013/14 4.9 6.7
2014/15 5.1 4.1
2015/16 5.3 4.0
2016/17 5.6 5.5
2017/18 5.9 5.2
2018/19 6.4 8.1
2019/20 6.8 6.8

Hospital admissions due to poisoning by drug misuse – break in time series 2012/13

Table 4.1 presents a time series of hospital admissions with a primary diagnosis of poisoning by drug misuse (controlled substances). In 2012/13 the ICD 10 code T40.4 was updated to include the prescription drug Tramadol, which at the time was not classified as a controlled substance. As such code T40.4 was initially excluded from the measure from that time. However, a 2014 amendment to the Misuse of Drugs Act added Tramadol as a controlled substance, and so code T40.4 has now been restored to the analysis for the full time series. However, this does create a break in the time series in 2012/13, with the change to code T40.4 adding a significant number of admissions: T40.4 admission count in 2011/12 = 283; in 2012/13 = 3,342.

Trade-offs between output quality components

This dimension describes the extent to which different aspects of quality are balanced against each other.

Most previously published sources referenced in this report include a methodology section which will contain specific information about trade-offs.

New analyses by NHS Digital consist of HES statistics. HES data quality information, including details of trade-offs, is available here:

The processing cycle and HES data quality - NHS Digital

Assessment of user needs and perceptions

This dimension covers the processes for finding out about users and uses and their views on the statistical products.

The compendia reports on drug misuse, alcohol, smoking and obesity were subject to a National Statistics consultation in 2016. The report on the findings of the consultation and the NHS Digital response are available at:

Consultation on Lifestyles Compendia Reports

A further consultation is planned for 2021 to look at possible opportunities for streamlining production of the compendia reports.

NHS Digital is keen to gain a better understanding of the users of this publication and of their needs; feedback is welcome and may be sent to (please include ‘Statistics on Drug Misuse’ in the subject line).

Performance, cost and respondent burden

This dimension describes the effectiveness, efficiency and economy of the statistical output.

All data used within this report is either already published or is part of an existing dataset. Therefore, no data is collected specifically for this report.

Confidentiality, transparency and security

The procedures and policy used to ensure sound confidentiality, security and transparent practices.

Some of the data contained in this publication are National Statistics. The code of practice for statistics is adhered to from collecting the data to publishing. The code of practice for statistics is available at: Code of Practice for Statistics

Supporting documents for statistical publications are available here:

Publications supporting user documents

Last edited: 7 December 2021 4:33 pm