This surprising article will probably change the way clinicians view and assess adult ADHD and the way DSM-6 conceptualizes it.
DSM-5 considers ADHD a “neurodevelopmental disorder” (page 32) and states that “ADHD begins in childhood” (page 61). Diagnostic Criterion B requires that “Several inattentive or hyperactive-impulsive symptoms were present prior to age 12 years.”
This study presents surprising, almost shocking, evidence to the contrary.
It’s a “prospective longitudinal study of a representative birth cohort”, namely “all infants born between April 1972 and March 1973 in Dunedin, New Zealand (N=1,037, 52% male, 7% non-Caucasian). Assessments “were carried out at birth and at ages 3, 5, 7, 9, 11, 13, 15, 18, 21, 26, 32, and, most recently, 38, when 95% of the 1,0007 study members still alive took part.”
Childhood ADHD was diagnosed in 61 children, for a cohort prevalence of 6%; adult ADHD was diagnosed at age 38 in 3%.
This is the mind-blowing part: “Unexpectedly, childhood and adult diagnoses comprised virtually non-overlapping sets of individuals. Follow-forward from childhood ADHD to adult ADHD revealed that only 3 (5%) of the cohort’s 61 childhood cases still met diagnostic criteria at age 38.”
The follow-forward result is not that surprising. Other follow-up studies have shown that the great majority of childhood ADHD patients no longer meet the full ADHD diagnostic criteria in adult life, although they experience substantial life difficulties (few got a university degree, many struggled financially, suicide attempts, criminal convictions, etc). A meta-analysis reported that “only 16% of childhood ADHD cases continue to meet diagnostic criteria into their 20s”.
It’s the “follow-back” that is surprising. Of the 31 cases of adult ADHD at age 38, only 3 had ADHD in childhood.
So those with childhood ADHD (79% male, IQs 10 points below normal) did not continue to have adult ADHD, and those with adult ADHD (61% male, normal IQ) did not have childhood ADHD.
Amusingly, among “childhood ADHD cases, only 23% had parents who recalled that their child had core ADHD symptoms or was diagnosed with ADHD. Thus, 77% of documented childhood ADHD cases were forgotten 20 years later.” So, 77% false negatives.
So much for obtaining an accurate history of childhood ADHD from parental informants. In addition, 4% of the comparison subjects’ parents (35 in all) “recalled evidence their child had ADHD”. So, 4% false positives.
Why so high? Perhaps because none of the children received medication, “as prescribing medication for ADHD was rare in New Zealand in the 1970s and 1980s.”
Specific medication treatment was also rare for ADHD in adults: only 4 of the diagnosed adults (13%) had taken appropriate drugs (Ritalin, Dexedrine, Strattera).
The adult ADHD patients had elevated (48%) rates of substance dependence on alcohol, cannabis and other drugs and persistent tobacco dependence (39%). 70% of them saw a mental health professional, and 48% were prescribed psychotropic medications, primarily for depression and anxiety.
What makes this study special is that it is “the first follow-back prospective study of the childhood origins of individuals diagnosed with DSM-5 adult ADHD”, and it revealed that “the adult syndrome did not represent a continuation from a child-onset neurodevelopmental disorder”.
This suggests that adult ADHD and childhood ADHD are two different disorders. Adult ADHD, in this study, appears not to have a childhood onset.
The authors make several interesting points:
- “Ubiquitous comorbidity for adults with ADHD has been reported before, suggesting the hypothesis that ADHD symptoms in adults in their 30s might be the psychiatric equivalent of fever, a syndrome that accompanies many different illnesses and is diagnostically nonspecific but signals treatment need.” (my emphasis)
- “A third intriguing possibility is that adult ADHD is a bona fide disorder that has unfortunately been mistaken for the neurodevelopmental disorder of ADHD because of surface similarities, and given the wrong name.”
- “Ironically, by requiring childhood onset and neurodevelopmental origins, DSM-5 leaves these impaired adults out of the classification system.”
- “If our finding of no childhood-onset neurodevelopmental abnormality for the majority of adult ADHD cases is confirmed by others, then the etiology for adults with an ADHD syndrome will need to be found.”
- “We suspect that, like us, clinicians often ignore the childhood-onset criterion for adult patients needing treatment.” (my emphasis)
This paper has huge implications.