To systematically identify published studies that examined LTOs (i.e., life consequences) of participants with untreated or treated ADHD, an extensive search of 12 literature databases was performed using a strategy based on the following inclusion and exclusion criteria. Only studies identified in these databases using electronic search engines and this search strategy were included. Studies including a group of participants with ADHD as determined by each study’s authors using any diagnosis criteria were included. To ensure a basic level of study quality, only peer-reviewed studies and only studies utilizing a comparator group (e.g., non-ADHD controls) or comparison measure (e.g., pre-treatment baseline) were included. Studies of participants that had received any or no ADHD treatment were included. Longitudinal studies with prospective follow-up or retrospective measures of 2
years or more, cross-sectional studies comparing participants of two ages differing by 2
years or more, or single cross-sectional studies of participants ≥10-years-old were included. Primary research articles published in English from January 1980–December 2010 inclusive, with available full-text were included. Studies examining symptoms only and not outcomes were excluded. Studies in which ADHD was not a primary condition of the study participants, but was secondary to another condition (e.g., intellectual disabilities or bipolar disorder), were excluded. Animal studies, case studies, and studies including only children younger than 2
years old were excluded. Meta-analyses and literature review studies were also excluded.
The search strategy for study identification was as follows. Inclusionary terms were: (1) names of the condition; ADD (captured all versions of ADHD), hyperkinesis or hyperkinetic, TDAH (trouble déficit de l’attention/hyperactivité in French or trastorno por déficit de atención con hiperactividad in Spanish, DAH (déficit de l’attention/hyperactivité in French or déficit de atención con hiperactividad in Spanish), DAA (déficit de l’Attention/activité in French or déficit de atención y actividad in Spanish), and (2) LTOs; long-term, longitudinal, education, degree, socioeconomic, salary, divorce, relationship, hobbies, criminality, arrest, incarceration, automobile, car, driving, citation, weight, obesity, suicide, drug abuse, addiction, substance abuse, alcoholism, and (3) comparator condition or group; control, proband, placebo, untreated, no treatment, pre-treatment, comparator, follow-up, normal, compare. Exclusionary terms were: (1) developmental, causal, or symptom terms; neuroanatomy, neuropathology, molecular, gene, development, etiology, preclinical, dose-finding, reaction time, and (2) unsuitable publication types; reprint, review, conference presentation. A more detailed explanation of the search methodology is available upon request. All references retrieved are included in the appendix.
To identify as many studies as possible, the search utilized 12 databases: Academic Search Premier, CINAHL, Cochrane CRCT (including EMBASE), Criminal Justice Abstracts, ERIC, MEDLINE, Military and Government collection, NHS Economic Evaluation database, PsycARTICLES, PsycINFO, SocINDEX, and Teacher Reference Center. Two search engines were used to search MEDLINE. Duplicates were eliminated electronically and manually. Additional unsuitable publication types were eliminated manually, including editorials, comments, reviews, non-peer-reviewed articles, and letters.
Based primarily on title and abstract, remaining studies were manually reviewed and included based on the agreement of two researchers. Each study’s data was extracted into a database; data collected included: (1) study location (country of origin), (2) study sample size, (3) study length, (4) participant’s age range, (5) study support, (6) diagnostic criteria, (7) study type (longitudinal, cross-sectional, prospective, retrospective), (8) outcome measures, (9) outcome results, (10) comparator type, (11) treatment type, and (12) treatment duration. Similar outcome measures were grouped together.
For the purpose of examining studies of ADHD originating in different geographical regions of interest, studies were grouped by location according to the UN Geoscheme (UN, 2011
). Major regions included Northern America (United States and Canada excluding Mexico), Europe, Eastern Asia, Western Asia, Oceania (New Zealand and Australia), and Latin America (including Mexico) and the Caribbean. International collaborations were also of interest.
For the purpose of examining studies of ADHD involving participants of different ages, the age range of participants was noted whenever possible and mid-range age was calculated. If the age range was not reported, the mean age was used. The mid-range/mean age was used to group each study into one of three age groups: children were 6- to 12-years-old, adolescents were between 13- and 17-years-old, and adults were above 17
years old. For mid-range ages 18–22, the minimum and maximum ages were also taken into account. If the minimum age was 16
years or younger and the maximum age was below 30
years, then the study was grouped with adolescent studies, rather than adult studies. For further analysis of studies of adults specifically, the age range/mean age was used directly to group studies into three adult groups: transitional adults (18- to 24-years-old), young adults (25- to 44-years-old), and mature adults (45- to 64-years-old).