The Swedish Twin Registry (STR) today contains more than 194,000 twins and more than 75,000 pairs have zygosity determined by an intra-pair similarity algorithm, DNA, or by being of opposite sex. Of these, approximately 20,000, 25,000, and 30,000 pairs are monozygotic, same-sex dizygotic, and opposite-sex dizygotic pairs, respectively. Since its establishment in the late 1950s, the STR has been an important epidemiological resource for the study of genetic and environmental influences on a multitude of traits, behaviors, and diseases. Following large investments in the collection of biological specimens in the past 10 years we have now established a Swedish twin biobank with DNA from 45,000 twins and blood serum from 15,000 twins, which effectively has also transformed the registry into a powerful resource for molecular studies. We here describe the main projects within which the new collections of both biological samples as well as phenotypic measures have been collected. Coverage by year of birth, zygosity determination, ethnic heterogeneity, and influences of in vitro fertilization are also described.

The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study targeting all twins born in Sweden since July 1, 1992. Since 2004, parents of twins are interviewed regarding the children's somatic and mental health and social environment in connection with their 9th or 12th birthdays (CATSS-9/12). By January 2010, 8,610 parental interviews concerning 17,220 twins had been completed, with an overall response rate of 80%. At age 15 (CATSS-15) and 18 (CATSS-18), twins and parents complete questionnaires that, in addition to assessments of somatic and mental health, include measures of personality development and psychosocial adaptation. Twin pairs in CATSS-9/12 with one or both twins screening positive for autism spectrum disorders, attention deficit/hyperactivity disorder, tic disorders, developmental coordination disorder, learning disorders, oppositional defiant disorder, conduct disorder, obsessive–compulsive disorder, and/or eating problems have been followed with in-depth questionnaires on family, social environment and personality, and subsequently by clinical assessments at age 15 together with randomly selected population controls, including 195 clinically assessed twin pairs from the first 2 year cohorts (CATSS-15/DOGSS). This article describes the cohorts and study groups, data collection, and measures used. Prevalences, distributions, heritability estimates, ages at onset, and sex differences of mental health problems in the CATSS-9/12, that were analyzed and found to be overall comparable to those of other clinical and epidemiological studies. The CATSS study has the potential of answering important questions on the etiology of childhood mental health problems and their role in the development of later adjustment problems.

The rate of autism spectrum disorders (ASDs) and brain abnormalities was analyzed in 31 individuals (15 males, 16 females; age range 1mo to 31y, mean age 8y 11mo) with CHARGE association, as part of a multidisciplinary study. A meticulous neuropsychiatric examination was performed, including standardized autism diagnostic interviews. Judgement regarding ASDs was impossible in three infants and three patients who were deaf and blind. Five individuals met diagnostic criteria for autism, five for an autistic-like condition, and seven for autistic traits. Brain abnormalities were indicated in almost three-quarters of examined individuals, and midline abnormalities of the forebrain in one-third. Awareness of the coexistence of CHARGE and ASDs is important in habilitation care in CHARGE. Moreover, the results indicate that a subgroup of ASDs may be associated with errors in early embryonic brain development.

The aim of this study was to assess prospectively the long-term outcome in a representative sample of teenage-onset anorexia nervosa (AN) in respect of psychiatric disorders and overall outcome. Fifty-one AN cases, recruited by community screening, with a mean age of onset of 14 years, was contrasted with 51 matched comparison cases at a mean age of 24 years (10 years after AN onset). All 102 cases had been examined at ages 16 and 21 years. At 24 years all probands were interviewed regarding psychiatric disorders (SCID-I) and overall outcome (Morgan-Russell assessment schedule, the GAF). There were no deaths at 10-year follow-up. One in four in the AN group had a persisting eating disorder (ED), including three who still had anorexia nervosa. Lifetime diagnoses of affective disorders and obsessive-compulsive disorder were over-represented in the AN group. Outcome according to Morgan-Russell was poor in 27%, intermediate in 29%, and good in 43%. According to the GAF, half the AN group had a poor psychosocial functioning. These were subjects with either a persisting ED or lifelong problems with social interaction or obsessive-compulsive behaviour. Ten-year outcome of teenage-onset AN is favourable in the majority of cases; most individuals have recovered from their ED and have no other axis I disorder. However, half the AN group reported poor psychosocial outcome, in most cases explained by a persisting ED or chronic obsessive-compulsive behaviour/social interaction problems.

Twenty-one individuals (19 females, two males) with teenage- onset anorexia nervosa (AN), 19 of whom were weight restored, were assessed using single-photon emission computed tomography (SPECT) 7 years after onset of AN, at a mean age of 22 years. For comparison we recruited a younger group without neuropsychiatric disorder (mean age 9:8 years; five females, four males) who underwent SPECT at follow-up after an operation for coarctation of the aorta or because of lymphatic leukaemia. Ethical considerations precluded the study of regional cerebral blood flow (rCBF) in participants with completely normal development. The group with AN showed marked hypoperfusion of temporal, parietal, occipital, and orbitofrontal lobes compared to the contrast group. rCBF was not correlated to body mass index in any of the groups. Results suggest that, even long after re-feeding has occurred, AN may be associated with moderate to severe cerebral blood flow hypoperfusion in the temporoparietal (or temporoparietooccipital) region and in the orbitofrontal region. A limitation of the study is that the young contrast group in this study could be expected to have a higher global rCBF than the group with AN. However, this should not significantly affect the relative values used in this study.

To study the development of physical health and some neuromotor functions in anorexia nervosa (AN) 51 individuals (48 females, three males) with a mean AN onset of 14 years, recruited after community screening, were followed prospectively together with 51 age-, sex-, and school-matched individuals without AN (controls). About 10 years after AN onset, all individuals were examined in respect of physical health and neurodevelopment. There were no deaths. Weight and height had normalised, except in three participants with persistent AN. Significantly more participants with AN had a physical complaint/disorder, including hirsutism. This might be a long-term complication in weight restored AN. Dysdiadochokinesis occurred almost exclusively among individuals with former AN in accordance with our previous studies.

The total population of 15-year-olds in Göteborg, Sweden, were screened in 1985 for anorexia nervosa using brief questionnaires, growth charts and individual school nurse reports. An accumulated frequency of anorexia of 0.84% for girls up to and including 15 years of age was obtained, with 85% of the cases fulfilling DSM–III–R criteria. Boys were affected just over one-tenth as often as girls. The frequency of anorexia nervosa appeared to be much higher in private than in comprehensive schools. The peak age of onset seemed to be 14 years.