ADHD and Serotonin

Serotonin (also called 5-HTP⁴) is a neurotransmitter alongside other neurotransmitters like dopamine and norepinephrine. Neurotransmitters are responsible for the transmission of nerve impulses between nerve cells. Serotonin is "manufactured" by an amino acid, tryptophan. Sufficient levels of tryptothan ensure that the correct amount of serotonin is available for the brain.

Serotonin is responsible for a person's mood by ensuring that you get enough sleep, control your anxiety levels and relieving a feeling of depro. A low serotonin level is associated with depression and symptoms like anxiety, fear, feelings of worthlessness and fatigue, irritability, impatience, impulsiveness, inability to concentrate and overeating. It has also been associated with the ability to learn and even with migraine⁴. Tension is therefore eased when serotonin is produced. My deduction therefore is: an increased occurrence of migraine might point to a possibility of low serotonin and eventually depression. Secondly, ADHD migh also affect Serotonin as ADHD are prone to anxiety, feeling down (depro) etc.

Dopamine is responsible for a person's movement, emotional response and the ability to experience pleasure and pain. It also makes people more talkative and excitable and is generally associated with ADHD. When dopamine is produced by the brain, we are more alert and can think and act more quickly.

Norepinephrine is associated with the "fight or flight" response of a person as it increases the rate and force of contraction of the heart and therefore increasing blood pressure¹.

We have noted that sufficient levels of Tryptophan ensure that sufficient level of Serotonin is available for the brain. Tryptophan indirectly helps regulate your appetite, sleep better and elevate your mood because it prevents niacin (B3) deficiency (associated with e.g. muscular weakness, lack of apetite⁷) and raises the serotonin levels in the body. Tryptophan is one of the 22 amino acids our bodies need. More specifically, tryptophan functions as a biochemical precursor for serotonin. Low levels of tryptophan will produce less serotonin. Tryptophan can be supplemented but is not recommended (google the story of EMS outbreak in 1989 in the US from a supplement developed by a Japanese manufacturer¹³). The main source of tryptophan is from our diet (see this site for tryptophan content).

In the treatment of depression, medication generally targets serotonin and norepinephrine. Apart from medication, one can increase the serotonin levels indirectly with dietary supplements. A high carbohydrate (carb) diet will produce a "quick fix" but is definitely not recommended as it has other side effects and can lead eventually to diabetes and obesity. High protein is also indicated as being able to increase serotonin, especially protein like chicken, turkey, salmon, tuna, cheese (see this site for a list of protein and their serotonin levels⁶). However, a high protein diet causes too much serotonin to be released in the blood and causes the brain not being able to absorb all that is available. To curb this, a 30gr portion of carbs helps more serotonin being absorbed which comes down to a balanced diet. Serotonin can also be raised by:

In the treatment of ADHD, medication (methylphenodate) generally targets dopamine. A recent study however, points to the close link between these two neurotransmitters and of a possibility that medication for depression (venlafaxine) might have a positive effect on ADHD. These studies have also indicated a possibility of methylphenodate medication working on serotonin and not only on dopamine^{11 & 10}.

From this short (laymen's) discussion, it is clear to me that there is a close relationship between ADHD characteristics and some of the symptoms of low serotonin levels. Jesica Johansson's¹² research has found that ADHD children has up to 50% less tryptophan. According to her, tryptophan helps with the production of dopamine, serotonin and norepinephrine (the 3 neurotransmitters). Other sources only states that tryptophan helps with the production of serotonin. Other research have already found a relationship between ADHD and serotonin. Therefore, according to Jesica Johansson: "Thus far the focus has mainly been on the signal substances dopamine and noradrenaline in the medical treatment of ADHD. But if low levels of serotonin are also a contributing factor, other drugs may be necessary for successful treatment." (Jesica Johansson)¹². This means that both serotonin and dopamine is related to ADHD. It also means that people with ADHD might have a more likelihood for depression because serotonin is associated with depression and ADHD characteristics.

Gromisch¹⁴ wrote a good article explaining the 3 neurotransmitters' interactions with ADHD. According to the DSM-V classifications there are 3 subtypes of ADHD (see here). According to her then:

Furthermore, other research indicated that serotonin is associated with impulse control and aggression - clearly a characteristic of ADHD. Serotonin is linked to conduct disorders and mood problems. Knowing which neurotransmitter is lacking,w ill assist in making the right decision in terms of medication.

One research¹⁰ by Duke University even states that the traditional medication for ADD/ADHD, Ritalin, might actually not be working on dopamine, but serotonin. According to this research, mice's serotonin levels increased with Ritalin and reduced hyperactivity while the same affect was not visible on the dopamine levels.

Another article⁹ associates ADHD with low serotonin levels by pregnant moms. According to Emily Deans, low serotonin levels during pregnancy may have contributed to a child having ADHD. Low serotonin in the father may also have contributed, but to a lesser extent than with the mother. In my opinion, genetics are still the major contributing factor but I'm open to this hypothesis. Maybe, if the hereditary genes are there, low serotonin levels during pregnancy will enhance the ADHD characteristics in a child.