Evolutionary advantages of ADHD traits

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Traits of ADHD Today

• Attention-Deficit / Hyperactivity Disorder
• Attention Problems
• Hyperactivity
• Impulsivity
• Impairment in ability to delay
• gratification

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Hunter in a farmers world

• ADHD as a different but not deficit profile
• Humans ancestors lived for a few million years
  in hunter-gather societies.
• Dramatic change in the last 10,000 years
• However because of the rapid rate of change
  evolution of the human genome has not caught up.

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So what were hunter societies like
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Problem solving world
Low motor activity
Resource-rich
Non-impulsive
Hypervigilant, high scan
Time optional
Unsafe, rapidly changing
Focussed attention, low scan
Safe, little change
Impulsive
Time-critical
Hyperactivity
Response ready
(Adapted from Jensen, 1997)
Resource-depleted
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Adaptive Functions
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Criteria for a function to be classed as adaptive

• Recurring characteristics over generations.
• Is present throughout the individuals life time.
• Genetic basis.
• Develops in a normal environment.
• Interacted with ancestral environment the
  adaptive problem.
• Offered best solution so genetically selected.
• By enhancing the reproduction of the individual.

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Does ADHD meet these criteria

• Occurs across generations.
• Present in adulthood.
• Cross cultural studies show that it is universal.
• The characteristics of ADHD are adaptive and
  therefore would promote the propagation of the
  hunter gene
• More opportunities for mating
• More likely to survive long enough

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The Genetics of ADHD

• Both DRD4 (dopamine receptor)
• SLC3A6 (dopamine transporter)
  reported in molecular genetic studies as linked
  with ADHD.
• One of the most replicated links in psychiatric
  genetics. (Maio, Grizenko and Joober, 2003).
• ADHD is polygenetic.

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SLC3A6 and ADHD

• Consistent with psychostimulant treatment.
• Knock-out mice
• Spontaneously hyperactive
• Higher levels of motor
• activity
• Significantly calmed
• by amphetamines

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DRD4 and ADHD

• DRD4 has approximately 10
• different versions (alleles).
• The 7R allele is associated with ADHD.
• 7R has a prevalence rate of 20.6 in the general
  population (Maio et al. 2003)
• People with ADHD are nearly twice as likely to
  have the 7R allele than non-ADHD individuals.
  (Faraone et al, 2001)

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Nature via Nurture

• ADHD has a genetic base.
• This does not refute the influence of social
  factors.
• Higher prevalence rates in deprived areas
• (studies cited in Taylor)
• Genetic behaviours are occurring due to an
  environmental cue. (Ridley, 2003)

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Is ADHD an Adaptation?

• It is extremely unlikely that ADHD could have
  evolved and been maintained by chance alone.
• ADHD effects functioning
• ADHD is a complex disorder
• ADHD is an Adaptation

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Are we just telling Darwinian stories?

• Can we really reverse engineer the mind?
• It is possible to create such an explanation for
  anything Females took longer to come down from
  the trees!
• Just so stories (Goldstein 1998) claim that the
  romantic idea of ADHD as an old evolutionary
  trait is nothing but fiction.
• ADHD not adaptive in any context.
• Does not fit with evolutionary theory.

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Continued

• Executive Function -
• Goldsteins Model
• Hunter-gatherer -
• Evolutionary Model

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Or is ADHD a spandrel?
Spandrels

• Gould and Lewontin, 1979

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Just-so-so-Stories

• Natural Selection does not
• mean an organism will be optimal.
• Natural Selection means that things that are only
  slightly advantageous will be kept.
• Therefore, the Hunter of the past would not have
  been the perfect hunter.
• ADHD may have held some advantages for a hunter
  in the past.

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Does America have ADHD?

• We are a supermobile hyperconected,
  media-saturated society (U.S. News)
• News sound bite 43s to 8s
• TV ads from 53s to 25s
• 15s ads are common place
• 201 messages a day

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Does America have ADHD?

• Start more projects than you finish, hate waiting
  in traffic, chronically late sound familiar?
• Forced to give continuous partial attention
• If we took control filtered all the information
  we receive would ADHD disappear ?

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Modern Hunters

• Modern hunters show ADHD behaviours.
  (Krynen cited in Hartmann,
  p59-60)
• Therefore symptoms can not be totally created by
  things such as advertising .
• Advertising and other social factors may serve to
  activate the gene(s) responsible for ADHD.

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Conclusions

• Positive view of people who would previously be
  perceived as disordered.
• Clinical value.
• Proof that it is not just a present day
  phenomenon.
• The pieces of the Jigsaw fit.
• BUT is this enough?

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References

• American Psychiatric Association. (1994).
  Diagnostic and statistical manual of mental
  disorders. (4th ed.) New York The Psychological
  Corporation.
• Faraone, S. , Doyle, A. E. , Mick, E.
  Biederman, J. (2001) Am. J. Psychiatry 158,
  1052-1057.
• Foust, S.J. (1994) Notes from Dr. Barkley's ADHD
  seminar. Online Available at
  http//users.rcn.com/peregrin.enteract/add/barkley
  .html (accessed February 13, 2004).
• Goldstein, S. and Barkley, R.A. (1998). ADHD,
  hunting and evolution just so stories. ADHD
  Report. 6(5), pp.1-4.
• Gould, S.J. and Lewontin, R.C. (1979). The
  spandrels of San Marco and the Panglossian
  paradigm a critique of the adaptionist
  programme. Proc. R. Soc. Lond. 205, pp.581-598.
• Hartmann, T. (1996). Beyond ADD hunting for
  reasons in the past and present. California
  Underwood Books.
• Hensby, C. and Braham, B. Hunter of the past.
  Online Available at www.adders.org/freeware/hun
  ter.htm/ (accessed February 13, 2004)

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References continued

• Jensen, P.S., Mrazek, D., Knapp, P.K., Steinberg,
  L., Preffer, C., Schowalter, J., Shapiro, T.
  (1997). Evolution and revolution in child
  psychiatry ADHD as a disorder of adaptation.
  Journal of the American Academy of Child and
  Adolescent Psychiatry, 36(12), pp.1672-1679.
• Maio, S., Grizenko, N. and Joober, R. (2003).
  Dopamine genes and attention-deficit
  hyperactivity disorder a review. Journal of
  Psychiatry and Neuroscience, 28(1), pp. 27-38.
• Orr, H.A. (2003, Feb 27). Darwinian
  storytelling. The New York Review. Pp. 17-20.
• Pinker, S. (2002). The blank slate. London
  Penguin Books.
• Ridley, M. (2003). Nature via nurture genes,
  experience and what makes us human. London
  Fourth Estate.
• Schachar, R., and Sergeant, J.A. (2002).
  Classification issues. In Sandberg, S. ed.
  Hyperactivity and attention disorders of
  childhood, 2nd ed., pp. 126-161. Cambridge
  Cambridge University Press.
• Taylor, E. (1995). Syndromes of Attention
  Deficit and Overactivity. In Child and
  Adolescent Psychiatry modern approaches. 3rd ed.
  (Rutter, M., Taylor, E., Hersov, L., ed.s), pp.
  285-304. Oxford Blackwell Science.
• Zuckerman, M.B. (2001). Does America have ADD?
  U.S. News, 26th March, pp. 14