 [ Symptoms ] what causes generalized anxiety disorder gad [ Disease ] the exact cause of gad is not fully known but a number of factors    including genetics brain chemistry and environmental stresses    appear to contribute to its development genetics  some research suggests that family history plays a part in increasing the likelihood that a person will develop gad this means that the tendency to develop gad may be passed on in families brain chemistry  gad has been associated with abnormal levels of certain neurotransmitters in the brain neurotransmitters are special chemical messengers that help move information from nerve cell to nerve cell if the neurotransmitters are out of balance messages cannot get through the brain properly this can alter the way the brain reacts in certain situations leading to anxiety environmental factors  trauma and stressful events such as abuse the death of a loved one divorce changing jobs or schools may lead to gad gad also may become worse during periods of stress the use of and withdrawal from addictive substances including alcohol caffeine and nicotine can also worsen anxiety