Area-1255 Portal 2: Symptoms of Low Serotonin Levels (Signs / Symptoms of Low 5-HT Function / Availability / Levels)

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5-Hydroxytryptamine (5-HT) , also known as SEROTONin , is a powerul ancient chemical within the body that provides feedback to several other neurotransmitters and neuromodulators.
About 90% of it is in the gut, however, the 10-12% of it that is in the Brain and Spinal Cord is incredibly important and responsible for a number of effects on behavior, mood, and motivation, and especially, cognition.

Originally, it was thought that based on the benefits of SSRI'S, and based on the brain serotonin turnover rates of suicide victims, that low serotonin was the incidence that precedes a lot of the depressive behavior, and the subsequent studies on both animal and human behavior relative to serotonin levels, seemed to confirm the hypothesis that serotonin elevations are healthy for body and mind and especially for alleviating depression and Anxiety.

However, the last 5-10 years has instead shown that the picture is a lot more complex, including that...

Low Dopamine is more likely the cause of Depression, and that low Serotonin signaling is more likely a biochemical imbalance that relates back to both a dopamine deficiency but also a cortisol imbalance (ƒ).
High Serotonin, not low serotonin, causes Anxiety; including G.A.D, social anxiety (!), obsessive-compulsive symptomology (!), and contributes to panic. Benzodiazepines like Klonopine, Ativan & Xanax also work by reducing serotonin activity (!)
The observed efficacy of SSRI's is more likely a result of their interactions with other systems like BDNF, σ1-receptors (1) (2), and GABAergic interneurons (◊).
That any other serotonin actions relevant to SSRI's may accrue during years and be related to individual protein changes including the serotonin transporter protein. (○)

Regardless, there are still some mental health and Physical symptoms that DO have a direct connection to low Serotonin levels.

Mental Health Symptoms of Low Serotonin

Insomnia (3) (4) (this can happen with high serotonin as well, but for different reasons, low serotonin production can cause Insomnia by means of less melatonin availability, since serotonin is needed to convert into melatonin. High serotonin causes Insomnia by direct overstimulation of 5-HT1A/1B as well as 5-HT2A Receptors)
Impulsive & Aggressive Behavior (5) (6) (not equivalent to religious rantings or objective-oriented arguments/attacks, in fact, elevated serotonin is correlated with 'cult-leader-mentality' , showing that there are differences in impulsive-aggressive biochemistry versus goal-oriented and belief-oriented behaviors)
Reduced Fear-learning, Reduced Negative Responding to an Upcoming or Anticipated Negative Effect (7) (8) <-- Also includes reduced fear 'recognition'.....
High Libido, increased sexual risk-taking (9) (10)..
Strong Appetite, especially for carbohydrate foods, sugary soft-drinks and fatty foods like Bacon (11) (12) (13) (14)..
Gambling, and Risk-Taking Behavior in General <see Here>
Workaholicism or Perfectionism (!) (!) (though this can be explained by high serotonin as well, low serotonin types like things tidy, and visually orderly, and are more linear minded than high serotonin individuals, who often occupy a more scatterbrained environment)

Physical Symptoms of Low Serotonin

Perhaps the most remarkable effect, or 'side-effect, of low serotonin, is Constipation (!) - as serotonin is heavily involved in gastrointestinal motility and enterokinetic nerve function (!) (!!).
A Low, or High Heart Rate may be present with low serotonin, with a higher chance of being slightly faster than your average person (15) (16) (17) (18).
Low or High Blood Pressure, depending on secondary factors, for example low serotonin and normal or low noradrenaline would equal hypotension or low-end of normal blood pressure, but low serotonin and high noradrenaline may lead to higher calcium entry into cells, which may lead to higher sympathetic nervous system activity and higher blood pressure. (19) (20)
Migraine or Vascular Headaches [!] (( Not everyone will experience these effects, in fact, not even 30% may experience a migraine if they have no prior history of it, at least not without other factors setting in.))

SPECIFIC SEXUAL EFFECTS OF LOW SEROTONIN

Premature Ejaculation (21) (22) (23)
Increased ' Flaccid Hang ' Size (24) (25)
Quick Sexual Arousal (26) (27)
Loss of Selectivity in Partners, or Excessive / Persistent Experimentation with Sexual Acts (28) (29) (30) (31) (32) ...