Table 2.
Description of Outcomes Measured During the Transition to Adulthood, at Age 18 Years
| Measure | Informant | Description | Prevalence, % | Reference |
|---|---|---|---|---|
| Personality | Coinformants | At age 18, study members nominated two people “who knew them well.” Coinformants—mostly parents and cotwins—described each study member using a 25-item version of the Big Five Inventory. 99.3% of study members had data from at least one coinformant. 83% had data from 2 coinformants. We standardized and averaged data from coinformants. | — | 40, 41 |
| Poor mental health | ||||
| Mental disorder diagnoses | ||||
| Conduct disorder | Participant | Based on DSM-5 criteria, assessed as part of a computer-assisted module. | 15.1 | 42, 43 |
| Alcohol use disorder | Participant | Based on DSM-5 criteria, evaluated in face-to-face interviews using DIS. | 27.8 | 42, 43 |
| Cannabis use disorder | Participant | Based on DSM-5 criteria, evaluated in face-to-face interviews using DIS. | 6 | 42, 43 |
| Depression | Participant | Based on DSM-5 criteria, evaluated in face-to-face interviews using DIS. | 20.1 | 42, 43 |
| Generalized anxiety disorder | Participant | Based on DSM-5 criteria, evaluated in face-to-face interviews using DIS. The 6-month symptom duration criterion was not required because of the young age of the study sample. | 7.4 | 42, 43 |
| Posttraumatic stress disorder | Participant | Based on DSM-5 criteria, evaluated in face-to-face interviews using DIS. | 4.4 | 42, 43 |
| Suicide attempts or self-harm | Participant | To assess suicide attempts, study members were asked whether they had tried to kill themselves or attempted suicide since age 12, using a life-history calendar. If they answered positively, further questions were asked to obtain details and establish intent to die. 3.8% of study members had attempted suicide. To assess self-harm, study members were asked whether they had ever tried to hurt themselves, to cope with stress or emotional pain, since age 12, using a life-history calendar. Individuals who endorsed self-harm were queried about methods. 10 behaviors were probed (eg, cutting, burning, overdose), plus the option to describe any other way they had hurt themselves. 13.6% of study members had harmed themselves. | 14.3 | 28, 44 |
| Service use for behavioral or emotional problems | Participant | At age 18, study members reported whether they had accessed support services (eg, mental health professionals, medical doctors, or social services), spent time in the hospital, or had taken medication for dealing with emotional or behavioral problems in the past year. | 17.2 | 45 |
| Coinformant reports of poor mental health | Coinformants | Coinformants completed a questionnaire that included 10 items querying about study members’ mental health within the previous 12 months (example items: “Feels depressed, miserable, sad, or unhappy”; “Has alcohol problems”). We created a binary measure indicating whether both coinformants had endorsed one or more symptoms of poor mental health. | 30.4 | |
| Poor functional outcomes | ||||
| Low educational qualifications | Participant | Indicates whether study members reported that they did not obtain or scored a low average grade on their GCSE, a standardized examination taken at the end of compulsory education at age 16 years | 21.9 | |
| NEET status | Participant | Indicates whether study members were NEET, based on reporting that they were not studying, working in paid employment, or pursuing a vocational qualification or apprenticeship. | 11.6 | 46 |
| Cigarette smoking | Participant | Indicates whether study members reported that they were currently smoking daily. | 22.3 | |
| Risky sexual behavior | Participant | Indicates whether study members reported that they had engaged in two or more of the following risky sexual behaviors: having had sex before age 16; having had three or more sexual partners; practicing safe sex only sometimes or never; usually or always having sexual intercourse after a night out involving a lot of alcohol and/or drug use; having been told by a doctor that they had a sexually transmitted disease; and having had sexual relations resulting in pregnancy. | 25.8 | 47 |
| Social isolation | Participant | Study members were asked about their access to supportive relationships with family and friends using the MSPSS. The scale scoring was reversed, and social isolation was defined as being among the 20% highest scoring study members. | 20.0 | 48, 49 |
| Low life satisfaction | Participant | Study members were asked about their life satisfaction using the Satisfaction With Life Scale. The scale scoring was reversed, and low life satisfaction was defined as being among the 20% highest scoring study members. | 18.7 | 49, 50 |
| Official crime record | Official records | Official records of participants’ cautions and convictions beginning at age 10 through age 19 were obtained through United Kingdom Police National Computer record searches conducted in cooperation with the Ministry of Justice. | 10.2 | 49 |
| Victimization during adolescence | Participant | Participants were interviewed about exposure to a range of adverse experiences between 12 and 18 years using the JVQ-R2, adapted as a clinical interview. Exposure to victimization was coded on a 3-point scale (0, no exposure; 1, probable or less severe exposure; 2, definite or severe exposure). Individuals who reported a definite or severe level of exposure were coded as positive. Our adapted JVQ comprised 45 questions covering 7 different forms of victimization: maltreatment (3.3%), neglect (2.2%), sexual victimization (2.6%), family violence (12.1%), peer/sibling victimization (15.6%), cyber-victimization (6.5%), and crime victimization (19.3%). | 51, 52, 53 |
Note: DIS = Diagnostic Interview Schedule; GCSE = General Certificate of Secondary Education; JVQ-R2 = Juvenile Victimization Questionnaire, 2nd revision; MSPSS = Multidimensional Scale of Perceived Social Support; NEET = not in education, employment, or training; PNC = Police National Computer.