<unk>  <unk>  is a descriptive term which is used to better identify what appears to be a homogeneous group within the ADHD predominantly inattentive (ADHD-I or ADHD-PI) classification in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition.  It has been estimated that the<unk>  population may make up 30-50% of the ADHD-PI population.
In many ways, those who have an<unk>  profile have the opposite symptoms of those with classic ADHD: Instead of being hyperactive, extroverted, obtrusive, and risk takers, those with<unk>  are passive, daydreamy, shy, and "HYPO"-active in both a mental and physical way. They also don't have the same risk factors and outcomes. Their demeanor is<unk> , as if "in a fog." and logically they also process information more slowly. A key behavioural characteristic of those with<unk>  symptoms is that they are more likely to be lacking motivation. They lack energy to deal with mundane tasks and will consequently seek things that are mentally stimulating because of their underaroused state. Those with<unk>  symptoms show a qualitatively different kind of attention deficit that is more typical of a true information input-output problem, such as memory retrieval and active working memory. Conversely, those with the other two subtypes of ADHD are characteristically excessively energetic and have no difficulty processing information.
Sluggish cognitive tempo
Challenging behaviour
Inattention
Disorder of written expression
Jealousy
Excessive daytime sleepiness
Intrusive thoughts
Blunted affect