Typically, the progression of HD is divided into five stages. Each stage marks a change in situation or
loss of the ability to perform a particular task.
As HD progresses, an individual as well as his/her family are continually challenged to adjust to the loss
of ability that generally occurs at each stage. As HD damages more neurons in the brain, behavior changes occur as well as
changes in cognitive and motor ability. To read about how changes in the brain affect the motor symptoms of HD, click here.
During the early stages of HD, irritability, depression, anxiety and aggression are common behavior symptoms.
In the later stages, individuals tend to be less irritable and aggressive, as apathy and a lack of concern become more pronounced.
Disinhibition, often a problem while the person with HD is still active, also tends to diminish as apathy
sets in. During the late stages of HD, there appears to be some loss of self-awareness, and individuals tend to be less aware
of others feelings as well.
An analysis of the data obtained in the largest and most comprehensive study on the behavioral
symptoms of HD revealed that depression tends to occur sporadically and can occur at any time throughout the course of the
In this study, depression occurred with almost equal frequency at all stages of HD. The
data also indicate that irritability, inflexibility, preoccupations and verbal and physical aggression occur most frequently
in patients 6-11 years after the onset of HD.
It is important to note that the occurrence of certain behavioral symptoms during certain stages is just
a general trend and by no means absolute. Also, there is no association between duration of HD and severity of the behavior.
However, the data obtained in the aforementioned study suggest that there may be one exception to this rule.
Apathy, which is characterized primarily by lack of initiative, increased in severity with duration of illness.
Thus, it is possible that apathy may provide a useful behavioral marker of the progressive neurodegeneration of HD.