What was once considered psychological healthy (or at least not unhealthy) is now considered to be mental illness. Some of the behaviors, thoughts, and feelings that were within the then-normal range of human experience are now deemed to be in the pathological part of the continuum. Thus, the actual definition of mental illness has broadened, creating a bigger tent with more people under it. This explanation implies that we, as a culture, are more willing to see mental illness in ourselves and in others.
The increasing prevalence is in part because each edition of the DSM has increased the overall number of disorders. The DSM-I, from 1952, listed 106; the DSM-III, from 1980, listed 265, and the current DSM-IV has 297. (Complaints about this ever-increasing total led the chair of the DSM-5 task force, David Kupfer, to announce that the total number of disorders in DSM-5 will not increase. One way to add new diagnoses—and DSM-5 will—but not increase the total is to make a disorder in a previous edition into a “subtype” of another disorder in the new edition, thereby keeping two diagnostic entities, but with one subsumed under another.)
The increasing number of disorders comes about because some “problems” that were not previously considered to be mental illness were reclassified as such by their inclusion in the DSM—and it is the DSM that functionally defines mental illness in the United States.
As an example, prior to the DSM-IV, there was no diagnosis of Asperger’s syndrome; rather, people with what is now called Asperger’s would have been diagnosed with autism (“high functioning” autism) or not diagnosed at all. This syndrome was added as a separate disorder to highlight the different forms that autism symptoms may take and to focus research on the most effective treatments for Asperger’s. Others, however, claimed that the diagnostic label pathologized quirkiness. (In DSM-5, Asperger’s is classified as a subtype of a newly consolidated single diagnosis “autism spectrum disorder.”)
Some of the disorders added to DSM editions are primarily—or wholly—medical in nature. One example is the diagnosis of “breathing-related sleep disorder,” which arises from medical problems that interfere with sleep. One such medical problem is obstructive sleep apnea, which occurs when the muscles of the throat relax so much during sleep that they narrow or block the airway. Throughout the night, people with obstructive sleep apnea have their deep sleep cut short as they relax because they stop breathing; once in a lighter phase of sleep, they breathe normally again. This disorder is not a mental disorder, but a medical one.
Another example is the “disorder” “caffeine intoxication,” characterized by at least five symptoms after consuming the equivalent of two to three cups of coffee: restlessness, gastrointestinal problems, difficulty sleeping, nervousness, and rapid heartbeat. To meet the diagnosis, the symptoms must impair functioning in some way. It’s hard to believe that an episode of too much coffee or Red Bull constitutes a mental disorder, but there you have it. DSM-5 has added “caffeine withdrawal” as a diagnosis—characterized by a withdrawal headache plus at least one other symptom, such as drowsiness, that interferes with some aspect of functioning. With disorders like this in the DSM, it’s no wonder that half of Americans will have a diagnosable disorder in their lifetimes. The wonder is why more Americans won’t!