Output path

SQL:[IDI_Community].[cm_read_adhd].[ADHD_YYYYMM]
SAS: libname cmid dsn=idi_community_srvprd schema=cm_read_ADHD; run ;
How to access a code module in the Data Lab:Read here

Description

The purpose of this code module is to identify individuals in New Zealand in the IDI who have a recorded diagnosis of ADHD or records indicating an ADHD diagnosis is likely (for example pharmaceutical use).

The dataset will list individuals, the earliest event when an individual has a recorded/likely diagnosis of ADHD in the IDI, date of the earliest event, the individual’s age and whether they are alive at the time of the IDI refresh. For those individuals who have died, the dataset lists a date of death and age at death.

This module is not intended to be used to give a true prevalence rate of people in New Zealand with ADHD due to limitations of the datasets included in the IDI. The code module allows researchers to have a consistent way of identifying people with ADHD and will allow for comparisons of outcomes for people with ADHD and people without ADHD.

Key Concepts

• Individuals are identified from a diagnosis recorded using a recognised ICD-9-CM-A diagnosis code for ADHD or a diagnosis/likely diagnosis recorded through other means by a professional.
• An individual may have multiple entries in a source dataset or across a number of source datasets.
• This module collates the earliest reference to the individual with an appropriate diagnosis/likely diagnosis in each source dataset and then identifies the earliest reference amongst all datasets.
• The module indicates whether the individual was alive at the time of the most recent IDI refresh.
• The module will record events within the time period that data is included in the IDI.
• The earliest date recorded in the IDI is not a date of diagnosis or onset of a condition.

Business history

Code history and ICD code notes

ICD codes used are based on the ICD clinical code system for the earliest date of data as per Health New Zealand (HNZ) | Te Whatu Ora best practice. This means ICD-9-CM-A codes have been used in line with the start of the health-related datasets in the IDI.

On advice from HNZ clinical coding/classification staff, codes have first been looked up directly in ICD-10-AM 12th Edition (current Edition used), then back mapped to ICD-10-AM 1st Edition and then back mapped to ICD-9-CM-A codes.

ICD-9-CM-A codes have also been added to ensure coverage if the diagnosis was coded in ICD-9-CM-A using the latest ICD classification definitions (see Table 1).

References

1. Beltran-Castillon L and McLeod K (2023) From Data to Dignity: Health and Wellbeing Indicators for New Zealanders with Intellectual Disability. Published: IHC, Kōtātā Insight
2. Stats NZ (2025) Household Disability Survey 2023 - findings, definitions, and design summary.
3. New Zealand Formulary (2025) Release 153 - 1 March 2025.
4. Ministry of Health (2024) New Zealand Health Survey 2023/24 - Annual Data Explorer.

Community of Interest

Key business rules

Table 1: ICD-9-CM-A codes included to ensure coverage if coding in ICD-9-CM-A – includes forward/backward map to ICD-10-AM 1st Edition

To ensure coverage when using ICD-9-CM-A codes, the following codes are noted to forward/backward map to ICD-10-AM 1st Edition.

Note:
Forward mapping provides equivalent codes for deleted codes in the newer edition.
Backward mapping provides equivalent codes for new codes in the newer edition.

Data quality and other known issues

1. Not all individuals in New Zealand diagnosed with ADHD will be identified in this module. The module requires that the individual has had an ACC claim form, hospital discharge events, received mental health or Disability Support Services, had their death recorded, where the diagnosis of ADHD has been specified, or relevant medication dispensed where an ADHD diagnosis is likely.

2. Datasets included have different lag times for having updated data available in the IDI. This means the completeness of the data at the time of analysis will depend on the lag time of the different datasets.

3. Individuals identified in the SOCRATES disability dataset do not always appear in the referral or needs assessment datasets as well. Where an individual is only identified through the SOCRATES disability dataset there is no associated event date. In this case a proxy date of ‘3999-12-31’ will be seen in the final table.

4. Registerable stillbirths are included in the mortality dataset.

Comparison against other sources

• Counts of individuals published in the IHC publication ‘From Data to Dignity’, (2023) were for those individuals with ADHD in the study population defined as the 2018 Administrative Population Census (APC). The counts from this code module for people with ADHD are higher than those in the 2023 publication.

• Counts from the latest Stats NZ Household Disability Survey (HDS) estimated 3% of the New Zealand population aged 5 years and over living in New Zealand households had a diagnosis of ADHD (Stats NZ, 2025). This equates to around 128,000 diagnoses. In comparison with the HDS, this module has a significantly lower count.

• Data from the 2023/24 New Zealand Health Survey (NZHS) estimates the prevalence of diagnosed ADHD in children aged 5 to 14 years old to be 5.3% (Ministry of Health, 2024). This module significantly undercounts for this age group.

Note:

When using this code module it is important to make sure to consider biases and limitations of the IDI data as well as biases and limitations that exist within health/health-related datasets. Some biases may include under-diagnosis, miss-diagnosis, cultural preference, systemic racism, clinician bias, policy changes, and data recording changes. These biases and limitations will vary for different groups and therefore have different effects on the resulting data and any analysis.

Parameters

The following parameters should be supplied to this module to run it in the database:

1. {targetdb}: The SQL database on which the datasets are to be created.
2. {idicleanversion}: The IDI Clean version that the datasets need to be based on.
3. {targetschema}: The project schema under the target database into which the datasets are to be created.

Dependencies

{idicleanrefresh}.[acc_clean].[claims]
{idicleanrefresh}.[acc_clean].[medical_codes]
{idicleanrefresh}.[moh_clean].[pub_fund_hosp_discharges_diag]
{idicleanrefresh}.[moh_clean].[pub_fund_hosp_discharges_event]
{idicleanrefresh}.[moh_clean].[priv_fund_hosp_discharges_diag]
{idicleanrefresh}.[moh_clean].[priv_fund_hosp_discharges_event]
{idicleanrefresh}.[moh_clean].[mortality_diagnosis]
{idicleanrefresh}.[moh_clean].[mortality_registrations]
{idicleanrefresh}.[data].[personal_detail]
{idicleanrefresh}.[dia_clean].[deaths]
{idicleanrefresh}.[moh_clean].[pop_cohort_demographics]
{idicleanrefresh}.[moh_clean].[pharmaceutical] 
{idimetadatarefresh}.[moh_pharm].[dim_form_pack_subsidy_code]

The following IDI_Adhoc are the most recent versions for this current refresh but changes to the code will need to be made as new datasets are uploaded into the IDI.

[IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_disability_2022]
[IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_needs_assessment_2022]
[IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_referral_2022]
[IDI_Adhoc].[clean_read_MOH_PRIMHD].[primhd_diagnoses_202502]
[IDI_Adhoc].[clean_read_MOH_PRIMHD].[moh_primhd_mhinc]

Outputs

{targetdb}.{targetschema}.adhd

Variable descriptions

Granularity:
One row represents an individual, the earliest identification of their diagnosis in the IDI, birthdate, gender and death (if applicable).

Module Version & Change History

Code

/*Set Parameters*/
/*Ref date should be the 15th of the month of the refresh used*/
:setvar targetdb
:setvar targetschema 
:setvar idicleanversion  
:setvar refdate
:setvar idimetadataversion

USE $(targetdb);
GO

/*ACC claims with a code that includes ADHD */

DROP TABLE IF EXISTS #acc_adhd;

SELECT
c.snz_uid
,'ACC' AS source_table
,c.code
,c.date AS event_date
,CAST(NULL AS VARCHAR(10)) AS entity
INTO #acc_adhd
FROM 
(
SELECT 
[snz_uid]
,[acc_cla_accident_date] AS date
,[acc_cla_primary_inj_code] AS code
FROM [$(idicleanversion)].[acc_clean].[claims]
      WHERE ([acc_cla_primary_inj_code] IN ('E2E00', 'E2E01', 'E2E0.') AND [acc_cla_primary_inj_type_code] = 'Read Code')
UNION ALL  
SELECT 
b.snz_uid
,b.acc_cla_accident_date AS date
,[acc_med_injury_code] AS code
FROM [$(idicleanversion)].[acc_clean].[medical_codes] AS a
     LEFT JOIN [$(idicleanversion)].[acc_clean].[claims] AS b ON a.[snz_acc_claim_uid] = b.[snz_acc_claim_uid] 
    WHERE [acc_med_injury_code] IN ('E2E00', 'E2E01','E2E0.') 
   ) AS c;

/*Publicly-funded hospital discharges where clinical code matches a diagnosis of ADHD*/

DROP TABLE IF EXISTS #moh_pub_adhd;
SELECT 
b.snz_uid
,'MOH_PUB' AS source_table
,a.[moh_dia_submitted_system_code]
,a.[moh_dia_diagnosis_type_code]
,a.[moh_dia_event_id_nbr]
,a.[moh_dia_clinical_code]
,b.moh_evt_birth_year_nbr
,b.[moh_evt_evst_date] AS event_date
,CAST (NULL AS VARCHAR(10)) AS entity
INTO #moh_pub_adhd
FROM [$(idicleanversion)].[moh_clean].[pub_fund_hosp_discharges_diag] as a 
	LEFT JOIN [$(idicleanversion)].[moh_clean].[pub_fund_hosp_discharges_event] as b ON a.moh_dia_event_id_nbr = b.moh_evt_event_id_nbr
    WHERE ((SUBSTRING(a.[moh_dia_clinical_code],1,5) IN ('31400', '31401') OR SUBSTRING(a.[moh_dia_clinical_code],1,4) IN ('3141', '3142', '3148', '3149')) AND a.[moh_dia_clinical_sys_code] = '06'
    AND a.[moh_dia_diagnosis_type_code] IN ('A','B'));

/*Privately-funded hospital discharges where clinical code matches a diagnosis of ADHD*/

DROP TABLE IF EXISTS #moh_pri_adhd;

SELECT
b.snz_uid
,'MOH_PRI' AS source_table
,a.[moh_pri_diag_event_id_nbr]
,a.[moh_pri_diag_clinic_sys_code]
,a.[moh_pri_diag_sub_sys_code]
,a.[moh_pri_diag_diag_type_code]
,a.[moh_pri_diag_clinic_code] 
,b.[moh_pri_evt_start_date] AS event_date
,CAST (NULL AS VARCHAR(10)) AS entity
INTO #moh_pri_adhd
FROM [$(idicleanversion)].[moh_clean].[priv_fund_hosp_discharges_diag] AS a
     LEFT JOIN [$(idicleanversion)].[moh_clean].[priv_fund_hosp_discharges_event] AS b ON a.moh_pri_diag_event_id_nbr = b.moh_pri_evt_event_id_nbr
     WHERE ((SUBSTRING(a.[moh_pri_diag_clinic_code],1,5) IN ('31400', '31401') OR SUBSTRING(a.[moh_pri_diag_clinic_code],1,4) IN ('3141', '3142', '3148', '3149')) AND a.[moh_pri_diag_clinic_sys_code] = '06'
     AND a.[moh_pri_diag_diag_type_code] IN ('A','B'));

/*Registrations in the mortality dataset where clinical code matches a diagnosis of ADHD*/

DROP TABLE IF EXISTS #mos_adhd;

SELECT
b.[snz_uid]
,b.[snz_moh_uid]
,'MOH_MOS' AS source_table
,DATEFROMPARTS(b.moh_mor_birth_year_nbr,b.moh_mor_birth_month_nbr,15) AS event_date
,a.[moh_mort_diag_clinical_code] AS code
,a.[moh_mort_diag_clinic_type_code]
,a.[moh_mort_diag_clinic_sys_code]
,a.[moh_mort_diag_diag_type_code]
,CAST (NULL AS VARCHAR(10)) AS entity
INTO #mos_adhd
FROM [$(idicleanversion)].[moh_clean].[mortality_diagnosis] AS a
     LEFT JOIN [$(idicleanversion)].[moh_clean].[mortality_registrations] AS b ON a.[snz_dia_death_reg_uid] = b.[snz_dia_death_reg_uid]
     WHERE ((SUBSTRING(a.[moh_mort_diag_clinical_code],1,5) IN ('31400', '31401') OR SUBSTRING(a.[moh_mort_diag_clinical_code],1,4) IN ('3141', '3142', '3148', '3149')) AND a.[moh_mort_diag_clinic_sys_code] = '06')
     OR (SUBSTRING(a.[moh_mort_diag_clinical_code],1,4) IN ('F900', 'F909', 'F901', 'F908') AND a.[moh_mort_diag_clinic_sys_code] >= '10');

/* Individuals in the Ministry of Health SOCRATES database with code 1201. Date can either be first contact date or referral date.*/

DROP TABLE IF EXISTS #moh_soc_adhd;
SELECT
DISTINCT
b.snz_uid
,'SOC' AS source_table
,CASE WHEN CAST(SUBSTRING(c.[FirstContactDate],1,7) AS date) IS NOT NULL THEN CAST(SUBSTRING(c.[FirstContactDate],1,7) AS date) 
	  WHEN CAST(SUBSTRING(e.[ReferralDate],1,7) AS date) IS NOT NULL THEN CAST(SUBSTRING(e.[ReferralDate],1,7) AS date)
	  WHEN CAST(SUBSTRING(e.[ReferralDate],1,7) AS date) IS NULL AND CAST(SUBSTRING(c.[FirstContactDate],1,7) AS date) IS NULL THEN '3999-12-31'
	  END AS event_date
,CAST (a.code as VARCHAR(7)) AS code
,a.[Description] 
,CAST (NULL AS VARCHAR(10)) AS entity
INTO #moh_soc_adhd
FROM [IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_disability_2022] AS a 
      LEFT JOIN [$(idicleanversion)].[moh_clean].[pop_cohort_demographics] AS b ON a.snz_moh_uid = b.snz_moh_uid 
      LEFT JOIN (SELECT DISTINCT snz_moh_uid,[FirstContactDate] FROM [IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_needs_assessment_2022] ) AS c ON a.snz_moh_uid=c.snz_moh_uid 
      LEFT JOIN (SELECT DISTINCT snz_moh_uid,[ReferralDate] FROM [IDI_Adhoc].[clean_read_MOH_SOCRATES].[moh_referral_2022]) AS e ON a.snz_moh_uid=e.snz_moh_uid
      WHERE code IN ('1201');

/*ADHD diagnosis in PRIMHD diagnosis data*/
DROP TABLE IF EXISTS #moh_PRIMHD_adhd;
SELECT
b.snz_uid
,a.[snz_moh_uid]
,'MOH_PRIMHD' AS source_table
,CAST (a.[organisation_id] AS VARCHAR(10)) AS entity
,a.[classification_code_id]
,a.[diagnosis_type]
,CONVERT(date,a.[classification_start_date],103) AS event_date
,a.[clinical_coding_system_id]
,a.[clinical_code] AS code
INTO #moh_PRIMHD_adhd
FROM [IDI_Adhoc].[clean_read_MOH_PRIMHD].[primhd_diagnoses_202502] AS a
     LEFT JOIN [$(idicleanversion)].[moh_clean].[pop_cohort_demographics] AS b ON a.snz_moh_uid = b.snz_moh_uid
     WHERE (((SUBSTRING(a.[clinical_code],1,5) IN ('31400', '31401') OR SUBSTRING (a.[clinical_code],1,4) = '3149')
     AND a.[clinical_coding_system_id] = '07' AND  diagnosis_type IN ('A','B','P'))
	 OR (SUBSTRING(a.[clinical_code],1,4) IN ('F900', 'F909', 'F901', 'F908') 
     AND a.[clinical_coding_system_id] = '10'));

/*ADHD diagnosis in PRIMHD MHINC data*/
DROP TABLE IF EXISTS #moh_mhinc_adhd;
SELECT 
b.snz_uid
,'MOH_MHINC' AS source_table
,CAST (a.[organisation_id] AS VARCHAR(10)) AS entity
,a.[classification_start] AS event_date
,a.[clinical_coding_system_id]
,a.[clinical_code] AS code
,a.[diagnosis_type]
INTO #moh_mhinc_adhd
FROM [IDI_Adhoc].[clean_read_MOH_PRIMHD].[moh_primhd_mhinc] AS a
     LEFT JOIN [$(idicleanversion)].[moh_clean].[pop_cohort_demographics] AS b ON a.snz_moh_uid = b.snz_moh_uid
     WHERE (((SUBSTRING(a.[clinical_code],1,5) IN ('31400', '31401') OR SUBSTRING (a.[clinical_code],1,4) = '3149')
     AND a.[clinical_coding_system_id] = '07' AND diagnosis_type IN ('A','B','P'))
	 OR (SUBSTRING(a.[clinical_code],1,5) IN ('31400', '31401') OR SUBSTRING (a.[clinical_code],1,4) IN ('3141','3149','3142','3148')
	 AND a.[clinical_coding_system_id] = '06' AND diagnosis_type IN ('A','B','P')));
	 

/* Pharmaceutical prescriptions for Atomoxetine, a sole indication pharmaceutical for ADHD. */
/* There are other pharmaceuticals prescribed for ADHD but these have multiple indications and are not included in this module.*/

DROP TABLE IF EXISTS #phh_adhd;
SELECT
c.snz_uid
,MIN(start_date) AS event_date
,MAX(end_date) AS end_date
,'PHH' AS source_table
,CAST (NULL AS VARCHAR(10)) AS entity
INTO #phh_adhd
FROM (
SELECT
a.[snz_uid]
,a.[moh_pha_dispensed_date] AS start_date
,CASE WHEN a.[moh_pha_days_supply_nbr] > 0 THEN DATEADD (DAY,a.[moh_pha_days_supply_nbr],a.[moh_pha_dispensed_date]) 
ELSE a.[moh_pha_dispensed_date]	
END AS end_date
FROM [$(idicleanversion)].[moh_clean].[pharmaceutical] AS a
      LEFT JOIN [$(idimetadataversion)].[moh_pharm].[dim_form_pack_subsidy_code] AS b ON a.[moh_pha_dim_form_pack_code] = b.[dim_form_pack_subsidy_key] 
      WHERE chemical_id IN (3887)
      ) AS c
	  GROUP BY snz_uid;
    

/* collate data from all sources into one table*/

DROP TABLE IF EXISTS #adhd;
SELECT
a.snz_uid 
,MIN(event_date) AS min_date
,source_table
,entity
INTO #adhd
FROM
(
SELECT  snz_uid, event_date, source_table, entity FROM #mos_adhd
UNION ALL
SELECT  snz_uid, event_date, source_table, entity FROM #moh_pub_adhd
UNION ALL
SELECT  snz_uid, event_date, source_table, entity FROM #moh_pri_adhd
UNION ALL
SELECT  snz_uid, event_date, source_table, entity FROM #moh_soc_adhd
UNION ALL
SELECT  snz_uid, event_date, source_table, entity FROM #moh_mhinc_adhd
UNION ALL
SELECT  snz_uid, event_date, source_table, entity FROM #moh_primhd_adhd
UNION ALL
SELECT snz_uid, event_date, source_table, entity FROM #acc_adhd
UNION ALL
SELECT snz_uid, event_date, source_table, entity FROM #phh_adhd
) AS a
GROUP BY snz_uid
, source_table
, entity;

/* subset of individuals who are deceased and are in death data*/

DROP TABLE IF EXISTS #adhd_dd;
SELECT 
a.*
,b.snz_birth_month_nbr
,b.snz_birth_year_nbr
,b.snz_sex_gender_code
,b.snz_deceased_year_nbr
,b.snz_deceased_month_nbr
,b.snz_birth_date_proxy
,NULL AS age
,DATEFROMPARTS(b.snz_deceased_year_nbr, b.snz_deceased_month_nbr, 15) AS dod
,'ADHD' AS [type]
INTO #adhd_dd
FROM #adhd as a
     INNER JOIN [$(idicleanversion)].[data].[personal_detail] AS b ON a.snz_uid = b.snz_uid
     WHERE a.snz_uid IN (SELECT DISTINCT snz_uid FROM [$(idicleanversion)].[dia_clean].[deaths])
     AND b.snz_deceased_year_nbr IS NOT NULL;

/* subset of individuals who are deceased but not in death data*/

DROP TABLE IF EXISTS #adhd_od;
SELECT
a.*
,b.snz_birth_month_nbr
,b.snz_birth_year_nbr
,b.snz_sex_gender_code
,b.snz_deceased_year_nbr
,b.snz_deceased_month_nbr
,b.snz_birth_date_proxy
,NULL AS age
,DATEFROMPARTS(b.snz_deceased_year_nbr, b.snz_deceased_month_nbr, 15) AS dod
,'ADHD' AS [type]
INTO #adhd_od
FROM #adhd AS a
     INNER JOIN [$(idicleanversion)].[data].[personal_detail] AS b ON a.snz_uid = b.snz_uid
     WHERE a.snz_uid NOT IN (SELECT DISTINCT snz_uid FROM [$(idicleanversion)].[dia_clean].[deaths])
     AND b.snz_deceased_year_nbr IS NOT NULL;

/* subset of individuals who are alive*/

DROP TABLE IF EXISTS #adhd_ad;
SELECT 
a.*
,b.snz_birth_month_nbr
,b.snz_birth_year_nbr
,b.snz_sex_gender_code
,b.snz_deceased_year_nbr
,b.snz_deceased_month_nbr
,b.snz_birth_date_proxy
,DATEDIFF(YEAR, b.snz_birth_date_proxy, '$(refdate)') AS age 
,'3999-12-31' AS dod 
,'ADHD' AS [type]
 INTO #adhd_ad
 FROM #adhd AS a
       INNER JOIN [$(idicleanversion)].[data].[personal_detail] AS b ON a.snz_uid = b.snz_uid
       WHERE a.snz_uid NOT IN (SELECT DISTINCT snz_uid FROM [$(idicleanversion)].[dia_clean].[deaths])
       AND a.snz_uid NOT IN (SELECT DISTINCT snz_uid FROM #adhd_dd)
       AND a.snz_uid NOT IN (SELECT DISTINCT snz_uid FROM #adhd_od);

 /* join all tables together*/

DROP TABLE IF EXISTS #adhd_final;
WITH adhd_union AS (
SELECT
* 
FROM #adhd_dd
UNION ALL
SELECT * FROM #adhd_od
UNION ALL
SELECT * FROM #adhd_ad
)

SELECT
* 
,DATEDIFF(YEAR, snz_birth_date_proxy, dod) AS age_at_death
,CASE WHEN age IS NOT NULL THEN 0 ELSE 1 END AS death_status
INTO #adhd_final
FROM adhd_union;

/* select all required variables */

DROP TABLE IF EXISTS #adhd_min;
SELECT 
snz_uid
,[type]
,entity
,source_table
,min_date
,snz_sex_gender_code
,snz_birth_month_nbr
,snz_birth_year_nbr
,snz_birth_date_proxy
,age
,death_status
,snz_deceased_year_nbr
,snz_deceased_month_nbr
,CASE WHEN dod = '3999-12-31' THEN NULL ELSE dod END AS dod
,CASE WHEN age_at_death >1000 THEN NULL ELSE age_at_death END AS age_at_death
INTO #adhd_min
FROM #adhd_final
;

/*take earliest recorded date for each snz_uid and create table */
DROP TABLE IF EXISTS #adhd_dbl;

SELECT 
snz_uid
,[type]
,entity
,source_table
,min_date
,snz_sex_gender_code
,snz_birth_month_nbr
,snz_birth_year_nbr
,snz_birth_date_proxy
,age
,death_status
,snz_deceased_year_nbr
,snz_deceased_month_nbr
,dod
,age_at_death
INTO #adhd_dbl
FROM #adhd_min a
WHERE min_date = (
SELECT MIN(min_date)
FROM #adhd_min b
WHERE b.snz_uid = a.snz_uid)
ORDER BY snz_uid;

/* remove duplicate snz_uid with the same minimum date but different entities or sources. Create table in IDI_Sandpit */

DROP TABLE IF EXISTS [$(targetdb)].[$(targetschema)].[adhd];

WITH cte AS 
(SELECT 
ROW_NUMBER() OVER(PARTITION BY snz_uid ORDER BY snz_uid DESC) AS rn
FROM #adhd_dbl)

DELETE FROM cte WHERE rn > 1;

SELECT 
snz_uid
,[type]
,entity
,source_table
,min_date
,snz_sex_gender_code
,snz_birth_month_nbr
,snz_birth_year_nbr
,snz_birth_date_proxy
,age
,death_status
,snz_deceased_year_nbr
,snz_deceased_month_nbr
,dod
,age_at_death

INTO [$(targetdb)].[$(targetschema)].[adhd]

FROM #adhd_dbl