disorders. Other diseases such as hyperthyroidism may exhibit symptoms similar to those of ADHD, and it is imperative to rule these out as well. Autism is sometimes mistaken for ADHD, due to impairments in executive functioning found in some people with autism. However, autism also typically involves difficulties in social interaction, restricted and repetitive patterns of behavior and interests, and problems with sensory processing, including hypersensitivity. Along with this, the quality of diagnosing an adult with ADHD can often be skewed being that the majority of adults with ADHD also have other complications, ranging from anxiety and depression to substance abuse. Formal tests and assessment instruments such as IQ tests, standardized achievement tests, or neuropsychological tests typically are not helpful for identifying people with ADHD. Furthermore, no currently available physiological or medical measure is definitive diagnostically. However, psycho-educational, such as the Continuous Performance Test (CPT), and medical tests are helpful in ruling in or out other conditions (e.g. learning disabilities, allergies) that may be associated with ADHD-like behaviors. The use of neuroimaging is also steadily increasing to help in an ADHD diagnosis. Some of these include: single-photon emission computed tomography (SPECT) positron emission tomography (PET) functional magnetic resonance imaging (fMRI) United States medical and mental health professionals follow the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association; the International Classification of Diseases (ICD) published by the World Health Organisation (WHO) is often used by health professionals elsewhere. Until recently ADHD in adults was considered as a continuation of child-onset ADHD. It is now established, however, that also an adult-onset version exists. In a large longitudinal study from 2015 it was found that 28 of the 31 persons who had an ADHD-diagnosis at the age of 38 never had received an ADHD-diagnosis when tested at the ages of 11, 13 and 15. Treatment As a first step, adults with ADHD should receive psychoeducation about ADHD, so they understand the diagnosis. This is vital to ensure that adults with ADHD can make informed decisions about their treatment, and has other benefits such as improved relationships with others. Treatment often begins with medication selected to address the symptoms of ADHD, along with any comorbid conditions that may be present. Medication alone, while sometimes effective in correcting the physiological symptoms of ADHD, will not address the paucity of skills which many adults will have acquired because of their ADHD