According to the Lubbock-Avalanche Journal, bipolar disorder is a common cause of irrational behavior, potentially leading to undesirable social consequences. People with bipolar disorder alternate between manic and depressive states. DoSomething.org states that psychosis and psychotic disorders also cause irrational behavior.
A study in the Journal of Neuroscience showed that mildly stressful situations can affect human perception in the same way life-threatening situations do. Stressful events such as financial losses can cause irrational behavior that is not linked to mental disorders, even though such events are not as serious as life-threatening situations. This happens because the brain's evolutionary development has prompted it to produce exaggerated responses to stress.