Most brain disorders increase the affected person's risk of getting mental health problems. Brain disorders can be stressful to cope with but also alter temperament, emotion and thought. The parts of the brain most affected in Huntington's disease, the basal ganglia, have a complex role in movement thinking and feeling so a wide range of difficulties can occur. Sometimes the mental changes are noticed before problems with movement. Problems with thinking including difficulty concentrating, remembering or reasoning things out also occur but in most cases such 'cognitive' problems are mild until the later stages and can seem worse than they are because of difficulties with communication.
Personality can change in a number of ways.
A previously outgoing person can be quieter, less sociable and less interested in things. A placid, careful person can become more volatile and temper prone and become impulsive. As the condition progresses, though, people become quieter and tend to dislike change. There is also a tendency to have an incomplete awareness of how disabling the condition has become. This and the resistance to change can make people very reluctant to agree to necessary changes in care or support.