<P> Caffeine's benefits are "related to its mild psychostimulant properties". Caffeine's widespread appeal is due primarily to its effect to increase alertness and cognitive arousal and diminish fatigue . In most people, caffeine has positive benefits like the alleviation of fatigue and heightened cognitive arousal . Caffeine also produces a wide range of other symptoms, including upregulation of the cardiovascular system ranging "from moderate increases in heart rate to more severe cardiac arrhythmia". However, what is less widely known is that caffeine can induce anxiety - like symptoms in individuals, particularly when consumed in excess . Studies show that consuming caffeine in "excess produces persisting insomnia, nervousness, and mood fluctuations". </P> <P> Additionally, studies show that caffeine consumption results in "subsequent dysregulation" of HPA axis function, which presents in anxiety - related behavior . When undergoing stress, the body activates a system - wide response mechanism known as the HPA axis . This stress signal begins at the level of the hypothalamus in the brain and undergoes subsequent amplifications throughout the body . This system succeeds in elevating blood levels of stress hormones, which results in the body shutting down secondary bodily processes, increasing hyperawareness, and readying the body for response to the perceived threat . Studies show that activation of this pathway is associated with "anxiety - related disorders such as panic disorder, post-traumatic stress disorder and generalized anxiety disorder". </P> <P> In cases of prolonged consumption of excess amounts of caffeine, studies show that individuals exhibit a reduced response to HPA axis activation by the hormone ACTH and a generalized increase in basal levels of stress hormone corticosterone . This led researchers to conclude that "caffeine consumption decreases adrenal gland sensitivity to ACTH . A blunted HPA response to psychological stress has been seen in humans with panic disorder compared to healthy controls following administration of a psychosocial test". </P> <P> Various populations exhibit varying degrees of susceptibility to anxiety - like symptoms when consuming caffeine . Most notably, those who suffer from preexisting anxiety - related disorders, those who suffer from ADHD, and adolescents are at greatest risk for experiencing caffeine - induced anxiety - like symptoms . Adolescents, particularly, are at increased risk for developing anxiety disorders and anxiety - related symptoms . Studies show that adolescents who consume caffeine chronically demonstrate "transient and sustained neurochemical and behavioral responses". This means that when caffeine is consumed regularly in excess amounts, adolescents display "more lasting effects on behavioral reactivity to psychologically stressful events" and are at increased "vulnerability to the development of psychiatric disorders" in the long term . </P>

Large doses of caffeine have been shown to produce panic attacks