Heritability of Psychotic Experiences in Adolescents and Interaction With Environmental Risk

This twin study investigates whether the heritability of psychotic experiences changes with increasing exposure to environmental risks in adolescents.

Olweus Bully/Victim Questionnaire at age 15, self-report. This includes 24, although only 16 were included in this study because the remaining eight items cover bullying perpetration. Participants are asked to rate how often particular forms of bullying have happened to them in the past two months, and can answer 'It has not happened to me in the past couple of months', 'only once or twice', '2 or 3 times a week', 'about once a week', or 'several times a week'. They are also asked how many students perpetrated the bullying ('mainly by 1', 'a group of 2-3', 'a group of 4-9', 'a group of 10 or more', or 'by several different students or groups of students') and how long it lasted. 1 involved with drugs. Participants could respond 'yes' or 'no' to each item. We did not account for how stressful each event was rated as.
participants answered either 'it has happened' or 'it has not happened'.
Tobacco Use A questionnaire about substance and drug use was sent to the TEDS participants. For each drug or substance, they were asked to report whether they had ever tried it or not. One item concerned tobacco.
As for TEDS, a questionnaire was devised and included an item about whether participants had ever tried tobacco or not. 5,6 Cannabis Use The same questionnaire used to assess tobacco use also included an item about cannabis use.
The same questionnaire used to assess tobacco use also included an item about cannabis use. [7][8][9] Birth Weight When the parents of the twins in TEDS were first contacted, they were asked to complete a questionnaire which provided background and demographic information, as well as some items about perinatal factors. Parents reported the twins' birth weights in grams. Participants are asked to answer the questions based on their feelings in the past month. These include daydreaming, confusion if too much happens at once, and difficulty in getting started with tasks. Each question can be answered 'yes' or 'no'. SPEQ Grandiosity 12,13 Self-Report 8 Participants are asked to answer the questions while considering the last month. The questions cover belief in a special mission, having many great ideas, and being more unique than everyone else. Questions are answered on a 0-3 Likert scale. SPEQ Anhedonia 14 Self-Report 10 Participants completed a measure of hedonia, however the items are all reversed so that the items cover anhedonia. Participants are asked to answer the questions in relation to the previous month. The items relate heavily to looking forward to things, such as eating at a restaurant. Questions are answered on a 0-5 Likert scale. SPEQ Negative Symptoms 15 Parent Report 10 Parents were asked to rate how strongly they agree or disagree with a number of statements in relation to the twins, with no reference to a particular period of time. Items include, among others, lack of emotion, lacking energy or motivation, and having few interests. Questions are answered on a 0-3 Likert scale. APSS (CATSS) Self-Report 7 Participants were presented with a number of questions, and asked how often they had experienced various psychotic experiences. These included feeling as though they are being spied on, being sent messages, being conspired against by others, and having visual hallucinations. Questions were not asked with reference to a particular period of time.