Impact of the proposed new examples
The Workgroup states that the reliability of the ADHD items was found unreduced in the field trials. However, adding the examples may change the rating of the symptoms and rating scales currently used to assess symptoms of ADHD will need to be revised accordingly. Furthermore, the psychometric properties of these scales will have to be retested. The added examples to DSM-5 will most likely increase the prevalence of ADHD.
The impact of the change of age of onset
There is a substantial evidence indicating that the age of onset by age 7 is not valid. There is no clinical difference between children identified as onset by age 7 versus later in terms of course, severity, outcome, or treatment response [8]. Another problem is assessing the correct age of onset, especially in adults, but this may hold true whether the limit is 7 or the proposed 12 years of age. Re-analysis of data from a British birth cohort published by the ageof-onset subcommittee suggests that the majority of children who had symptoms at age 12 also had symptoms at 7 years of age [16]. However, a population-based study indicated that only 50 % of adults with ADHD recalled the onset by age 7, whereas by age 12, 95 % recalled the onset [2]. Another proposed change is in regards of what should be present before the age of onset. DSM-IV requires impairment due to some symptoms of ADHD by the age of onset, but the proposal for DSM-5 only requires the onset of several symptoms (no mentioning of impairment) by the age of onset. These two proposed changes in age of onset in DSM-5 will most likely increase the prevalence of ADHD, especially in adults.
Change of the description of situational pervasiveness
Criteria for ADHD should be met in two or more settings, this requirement is unchanged. The clarification (e.g., at school [or work] and at home) from DSM-IV is changed into (e.g., at home, school or work, with friends or relatives, or in other activities). By this, symptoms at home are no longer a requirement. This change and adding more and broader examples may increase the prevalence of ADHD