Happiness

• The most well-known positive aspect of serotonin is its ability to inspire feelings of well being and happiness. It contributes to these positive feelings in several different ways. For example, preventing the breakdown of serotonin and related neurotransmitters in the brain with drugs is a treatment for depression. Other related conditions, like social phobias and anxiety disorders, can be treated in a similar way.
  
  

Deficiency

• In experiments on mice, turning off the centers in the body that produce serotonin have led to breathing difficulties, heart failure and consistent fatigue. In humans, low serotonin levels might contribute in some way to sudden infant death syndrome, an issue raised by low levels seen in postmortem studies, though what isd the exact cause of the low serotonin levels in infants remains an unknown.
  
  

Males

• Serotonin also has several important roles to play in the male body. In experiments by Professor E.A. Kravitz of the department of Neurobiology at Harvard Medical School, on lobsters, for example, injections of serotonin caused the lobsters to exhibit behavior demonstrated by a dominant animal. Octopamine, another neurotransmitter, causes the opposite effect, which would be subordinate behavior. A serotonin deficiency has also shown to negatively affect normal male mating behavior in animal studies by Professor C.M. Loer of the University of California Department of Biochemistry and Biophysics.
  
  

Injections

• Serotonin is present in the venom of several different stinging animals, including wasps. Scientists reason that since one of serotonin's roles in the body is to indicate bleeding, the concentrated injection of serotonin from the sting of a wasp tricks the body into thinking that there should be large levels of pain associated with the sting. This is one definite negative of serotonin.