Yes, energy drinks can cause nervousness and anxiety. There is a case report of a person who developed anxiety, irritability, restlessness, poor concentration, fidgetiness, and difficulty falling asleep for a four month period, after drinking 6 to 8 8oz energy drinks every day for the four months prior to developing symptoms (Berigan, 2005). In this case study, the caffeine consumption was 800mg per day. There was complete resolution of anxiety and somatic symptoms after the energy drinks were discontinued.
When caffeine intake is greater than 250mg per day and chronic, it can lead to caffeinism, which is a syndrome that includes symptoms of anxiety, nervousness, irritability, restlessness, tremulousness, muscle twitching, rapid breathing, palpitation, flushing, insomnia, and gastrointestinal disturbances (Victor et al., 1981). So these anxiety and physical symptoms that develop from caffeinism can mimic the symptoms of generalized anxiety disorder (GAD).
According to Consumer Reports, the 27 energy drinks tested ranged from 6mg to 242mg of caffeine per serving. In addition to caffeine, some energy drinks also include guarana, a botanical caffeine source, so this also contributes to the overall caffeine consumption.
It is therefore important to look at your consumption of energy drinks if you are experiencing anxiety symptoms, as the high content of caffeine in energy drinks may be causing your anxiety.
References:
An anxiety disorder secondary to energy drinks: a case report. Berigan T. Psychiatry (Edgmont). 2005 Oct;2(10):10.
Somatic manifestations of caffeinism. Victor BS, Lubetsky M, Greden JF. J Clin Psychiatry. 1981 May;42(5):185-8.
