Brain Functions

• People who undergo chemotherapy sometimes develop "chemo brain," which causes them to have problems with concentration, memory, cognitive thinking and other brain functions. In addition, some people may have trouble focusing on daily chores or work projects, multitasking or finishing sentences, according to the American Cancer Society.
  
  

Moods

• Before, during and after cancer treatment, some people feel anger, fear or frustration, which can cause them to withdraw from social situations, lash out at others around them or have rapid changes in mood.
  
  

Relationships

• Chemotherapy treatment can cause people to feel hopeless, helpless and alone in the world, according to the American Cancer Society. These feelings, along with others, can sometimes cause them to develop strained relationships with their friends and family.
  
  

Physical, Emotional Changes

• During radiation therapy and chemotherapy, people feel physical and mental fatigue, which may cause them to have less energy and feel depressed. They may also have problems sleeping, which can cause them to feel restless or become easily irritable.
  
  

Sexuality

• Cancer treatment can cause some men to become impotent and some women to feel pain or vaginal dryness during sex, according to the National Cancer Institute. Sexuality changes can cause men and women to either feel a lack of interest in sex or become more emotionally and sexually connected to their partner.