ADHD

-        attention deficit/hyperactivity disorder

-        Classified as a developmental disorder

-        3 different types

-        Inattentive type

-        Hyperactive/impulsive

-        Combined type

-        Diagnosis based on symptoms that have occurred over past 6 months, with an age of onset around <12 years

Essential features:

●      Persistent pattern of inattention

●      And/or hyperactivity-impulsivity

●      Must be shown to impact development in a clinically significant manner

Key features of ADHD

●       ADHD symptoms are not just limited to one place (school, for example), but appear no matter where the child is.

●      Context matters.  Signs of the disorder may be minimal or absent when the individual is under close supervision, receiving frequent rewards for good behavior, in a novel setting, or doing something interesting.

○      This can make the disorder challenging to diagnose, as the doctor’s office often meets all of the above criteria.

●      The issues associated with ADHD tend to create other problems in the child’s life.

○      Academic performance tends to suffer.  Social rejection is common as well.

○      Other comorbid disorders may also make it more challenging (e.g., ASD, OCD)

●      ADHD is not considered an intellectual disorder per se.  Nevertheless, mild delays in language, motor and social development are common in children with ADHD.

○      This could be a consequence of simply not paying sufficient attention to things.

DSM5 diagnosis criteria

Inattentive type: 6/9* symptoms required

●      Often distracted by extraneous stimuli

●      Had problems staying focused on tasks

●      Does not seem to listen when spoken to

●      Does not follow through on instructions

●      Has problems organizing tasks and work

●      Avoids or dislikes tasks that require sustained mental effort

●      Often loses things

●      Doesn’t pay close attention to details or makes careless mistakes

●      Forgets daily tasks

Hyperactive/impulsive type: 6/9* symptoms required

●      Fidgets with or taps hands or feet, or squirms in seat

●      Not able to stay seated

●      Runs or climbs where inappropriate

●      Unable to play or do leisure activities quietly

●      Always “on the go”

●      Talks too much

●      Blurts out answers

●      Interrupts or intrudes on others

●      Has difficulty waiting for turn

Combined type: requires 6/9 symptoms for both criterias

What causes ADHD?

-        Mixture of genetic, environmental factors as well as brain chemistry

Genetics of ADHD

●      Elevated in first-degree biological relatives of individuals with ADHD

○      1st degree biological are relatives that share 50% of their genetic material. Eg. Siblings and parents

●      Etiology of ADHD has been suggested to be up to 80% genetic this makes it one of the most heritable disorder

●      Strong overlap with genes for autism spectrum disorder

●      In spite of the strong evidence for a genetic link, research has not yet uncovered much in the way of specific genes that might be to blame

○      Weak associate have been found with genes for the Dopamine reuptake

●      No evidence that ADHD is caused by sugar

Behaviours of ADHD

●      Marshmallow experiment

●      Rewards have less of an influence

●        dual pathway model is a theory about ADHD suggesting dysfunctions in both systems

Prevalence of ADHD

●      Prevalence of ADHD is approximately 7.6% - recent 2023 meta-analysis

○      Male to female ratio is about 3:1

●      Adult ADHD may have a prevalence as high as 2.5%. Longitudinal studies of ADHD show that symptoms gradually reduce across the lifespan, but persist in 30-50% of cases.

○      Impulsivity and hyperactivity tend to drop off more than attention. Many adults continue to struggle with attention their entire lives.

●      ADHD prevalence appears to vary worldwide, though not by as much as is often

claimed.

●      North America, when considered as a whole, has higher rates of ADHD than most other places (South America and Africa being exceptions)

Prevalence of ADHD: importance of Culture

●      Difficult to separate from the cultural context

●      Current DSM5 diagnostic criteria still seems to be based largely on elementary school-aged north American boy

●      If ADHD occurs everywhere in the world, it would still only be diagnosable in certain cultural contexts.

○      Hyperactivity and inattentiveness would not be as much of a concern in times and places where children do not go to school.

○      On the other hand, in areas where academic achievement is prized above all else, even minor levels of inattentiveness and hyperactivity would seem pathological.

What areas of the brain are affected?

-        Frontal cortex, parietal lobe, and cerebellar regions

-        Lateral surface:

-        Dorsolateral prefrontal cortex

-        Ventrolateral prefrontal cortex

-        Parietal cortex

-        Medial wall:

-        Dorsal anterior midcingulate cortex

-        Striatum:

-        Caudate and putamen

-        Cerebellum

How are these brain areas affected?

-        Alerting network:

-        frontal , parietal cortex and thalamus interact and form the alerting network which supports attention

-        Prepares the body to respond to stimuli by changing its internal state

-        Alerting network is weaker in individuals with ADHD

-        Frontostriatal circuit

-        The ventral cingulate cortex and the dorsal anterior cingulate cortex control affective and cognitive components of executive control. Along with the putamen, nucleus accumbens and caudate nucleus they form the frontostriatal circuit

-        neural pathways that connect frontal lobe regions with the striatum and mediate motor, cognitive, and behavioural functions within the brain

-        In ADHD there are abnormalities in the frontostriatal circuits which extend to the amygdala and cerebellum

Treatment of ADHD

●      Despite the complexity of the ADHD diagnosis, the efficacy of the available pharmacological treatment options is actually quite good.

○      Drugs are effective in 70-90% of cases.

●      The most common pharmacological treatments for ADHD are drugs of the psychostimulant variety.  These have been in regular use since at least the 1970s.

●      Popular drugs include methylphenidate (Ritalin/Concerta), amphetamine (Adderall), and d-amphetamine (Dexedrine).

○      These drugs are given at low doses, in long-acting, slow-release formats that limit the “rush” that characterizes their illegal counterparts

How do they work?

-        ADHD medications target the dopamine system in the brain

-        ADHD medications, such as stimulants, increase the amount of dopamine in the brain by blocking the reabsorption of dopamine in the brain's synapses. This allows more dopamine to bind to receptors, which helps neurons communicate with each other.

Ethics of ADHD

●      b/c ADHD is mostly a disorder of childhood, its treatment requires special consideration

●      Is it often suggested that children are overmedicated or that  medication is used as a substitution for effective parenting/schooling

●      Children are not small adults, so studies of drug effects on adult brains cannot be safely generalized to children

●      Emerging data from animal studies of chronic psychostimulant treatment suggest that long term side effects may exist

○      Chronic methylphenidate treatment is young rats reduces the rewarding power of cocaine on adulthood

○      Chronic amphetamine treatment reduces dopamine terminals in the striatum of monkeys

●      ADHD symptoms do tend to improve on their own as the child ages. Should we just leave ADHD alone and let it resolve itself?

○      Academic and social success during childhood strongly influences the rest of the individual's life.