No information was obtained about the number of respondents who had actually abstained from caffeine at some point. Albeit few in number, survey studies have typically reported lower rates of withdrawal and associated problems than those found in experimental studies. It is plausible that survey studies may underestimate the true rate of caffeine physical dependence in the general population. First, many caffeine users probably avert potential withdrawal due to the ubiquitous and frequent use of caffeine and thus are completely unaware of their dependence on caffeine. Lastly, caffeine withdrawal symptoms may be misattributed to other causes or ailments.
Experimental studies provide the most compelling data about the severity of caffeine withdrawal.
The term substance dependence is also used to describe a clinical syndrome of drug dependence, which comprises a constellation of symptoms or behaviors linked to problematic drug use. Since the publication of DSM-IV , clinical evidence of a caffeine dependence syndrome has been accumulating. Three studies have directly addressed the generic DSM criteria for making a diagnosis of substance dependence. Four of the seven DSM-IV criteria that seemed most applicable to caffeine were assessed. Median daily caffeine intake of those fulfilling a drug dependence diagnosis was 357 mg, with a range of 129 mg to 2548 mg.