A new study of twins suggests that attention-deficit hyperactivity disorder (ADHD) is strongly linked to genes, and that it is less a clear-cut disorder than an extreme form of a trait, like blood pressure, that varies throughout the population.
But because they didn't, this suggests ADHD is not a clear-cut disorder and is rather the extreme end of a continuum of behaviors.
If ADHD were a clear-cut disorder that was either present or not, researchers would expect to find a higher heritability in the group with more symptoms, says Levy.
Other exclusion criteria were intravenous drug use with a lifetime diagnosis of dependency; depression occurring solely in relation to alcohol or substance abuse or depression only secondary to medical illness or medication, and a clear diagnosis of bipolar disorder, schizophrenia, schizo-affective disorder or acute or transient psychotic disorders in first or second-degree relatives.
The model was restricted, a priori, to a two-class solution to determine whether a clear distinction between disorders of abuse and dependence could be discerned.
The relationship between diagnosis and frequency of PES use is illustrated in table 2. In both groups, the proportion of patients with chronic psychosis increased and, those without a clear diagnosis, adjustment disorders or psychosis not otherwise specified, decreased with increasing frequency of use.
However, they may still find it difficult to regulate their emotions toward these patients whom they have to hospitalize and who suffer from a personality disorder, and not from a clear-cut psychiatric disorder.
1 4% of spontaneous cases have a clear underlying connective tissue disorder affecting the blood vessels.
Only a very small proportion (1 4%) have a clear underlying connective tissue disorder, such as Ehlers Danlos syndrome type 4 and more rarely Marfan's syndrome.
Zlatan Krizan, a professor of psychology at Iowa State University who tells people at social events that he "studies assholes for a living," says nailing down a clear definition of the disorder is tricky because it occurs on a spectrum.
