Article Type : Review Article
Authors : Rahman MA, Habiba U, Ullah M and Rani M
Keywords : Central Nervous System; Neuroendocrine; Neuro-Inflammation; Neurotransmitter; Neuro-Genetics
Suicide has become a social and global menace. It has
turned out among the leading causes of mortality worldwide. Though numerous
issues have been implicated with its occasion and prevention, neuro-biochemical
concern has been less pronounced. This article is the neuro-biochemical
cross-talk with suicide.
Suicide, a global burning issue, encompass multiple facets of causative
and affective factors [1]. Personal, social, mental, economical and
career-based issues of different sorts have been linked with suicidal trends
and practices [2]. Little concern has been focused on the neuro-biochemical
hallmarks of suicide, attempts to suicide and associated preventive measures.
Thus, the present article has been aimed at delving out the neuro-biochemical
implications of suicide followed by preventive recommendations.
Involvement of central nervous system in suicidal
attempt
Thirty-seven years long studies on the Danish suicide victims reveal
that the people suffering from neurological disorders are at 75% increased risk
of committing suicide than their healthy counterparts [3]. Neurological
disorders like Alzheimer’s disease (AD), dementia, Parkinson’s disease (PD),
stroke, epilepsy, head injury pose grave threat towards development of suicidal
tendency [3]. Besides, anxiety and depression are two alarming risk factors of
suicide [3].
Serotonin and serotonergic brain circuit
Serotonergic brain circuits have directly been implicated in depression
and suicide [4].
Decreased level of serotonin (5-hydroxy tryptamine, 5-HT) in the brain
is among the most notorious causes of anxiety and depression [5]. Level of
serotonin metabolite 5-hydroxy indole acetic acid (5-HIAA) in the cerebrospinal
fluid (CSF) also affects serotonergic activity [6]. Diminished serotonergic
activity leads towards increased aggressive and impulsive behaviour as well as
murderous and suicidal tendencies [7].
Norepinephrine
Role of norepinephrine (NE) has been found to be opposite of that of the
serotonin i.e. increased NE levels tends towards aggressive and suicidal
attempts and vice versa [8].
Dopamine
Level of dopamine have been positively correlated with aggression and
suicidal attempt [9].
Hypothalamic-Pituitary-Adrenal Axis
The neuroendocrine system, hypothalamic-pituitary-adrenal (HPA) axis
regulates the body’s response to stress [10]. It maintains the interactions
among brain serotonergic, noradrenergic, and dopaminergic systems [11]. Stress
induces the release of the
corticotrophin releasing hormone (CRH) that activates the HPA axis through
release of adrenocorticotropin (ACTH) from the pituitary [12]. Consequently,
corticosteroids are released from the adrenal glands that result in behavioural
alterations [12]. Hyperactivity of the HPA axis has been linked with the
suicidal behaviour [13].
Neuro-genetics
Increased expression of the 5-HT2A receptor in the pre-frontal cortex of
the suicide victims indicate the possible neuro-genetics link [14]. Also,
differential expression of the serotonin transporter (5-HTT) gene has been
observed in the brain autopsies of the suicide victims [15]. Similar anomalies
have been implicated in the genes of monoamine oxidase (MAO) and
catechol-o-methyl transferase (COMT) [16].
Neuro-inflammation
Neuro-inflammation is another hallmark of suicidal brain [17]. Abnormal level of neuro-pro-inflammatory factors have been observed in the brains of the suicide victims [18]. Besides, altered activities of the neuroglial cells, especially of the astrocytes, have been observed [19]. Abnormal morphology of the astrocytes such as increased cell body warrant attention [20].
Rate of suicide has been soaring worldwide. Time is up for
focusing on neuro-biochemical phenomena with a view to maintaining sound
physico-psycho state of the individuals. In this aspect, care should be taken
to let the neurobiochemical activities at their balanced and healthy state. Let
the health-care professionals, policy makers and care givers of the
neurologically ill persons be concerned and take necessary steps for the stated
concern.
Authors gratefully thank Jahangirnagar University and the
University Grants Commission (UGC) of Bangladesh for providing all the
supports.