Anxiety & Depression 5-HTTLPR DNA Test
Fee Schedule for Year 2020
|Test Type||Testing Time||Fee|
|Anxiety & Depression 5-HTTLPR DNA Test||2 to 4 weeks||RM1780Order Kit|
All orders received before 2pm are shipped out the same business day. All orders received after 2pm or on weekends or holidays are shipped out the following business day. 24/7 online status check and account management available for all tests.
Serotonin and the serotonin receptor
Serotonin is a neurotransmitter in the brain that contributes to feelings of pleasure and well-being. When serotonin is released from cells in the brain or neurons it sends out signals to be happy and content.
The serotonin transporter moves serotonin from the synaptic cleft into the presynaptic neuron, allowing serotonin recycling in a sodium-dependent manner. It is also important for maintaining functional neural circuits that connect the amygdala and the cingulate regions of the brain.
S-allele of the serotonin transporter aka the "Grouchy" gene
The S-allele is one of the two common variation in a region called the 5-HTTLPR of the SLC6A4 gene, which encodes the 5-HTT serotonin transporter. The S-allele ("grouchy" gene) is the short variant of 5-HTTLPR, as it contains only 14 copies of a repetitive sequence element, compared to the 16 copies in the long variant (L-allele).
This deletion results in lower production of the serotonin transporter, and smaller amygdala and cingulate regions – two brain regions involved in emotional responses. The S-allele is linked to an increased risk of grumpy or sad feelings, and an increased risk of a variety of psychological conditions like depression, bipolar disorder, attention deficit disorder and Alzheimer’s disease, as well as addictive behaviors and sudden infant death syndrome. This is why it is often referred to as the "grouchy" gene.
How is the S-allele inherited?
The SLC6A4 gene is located on an autosome (chromosome 17). Autosomes are inherited in pairs - one from each parent; hence people carry two copies of the SLC6A4 gene. Inheriting one or two copies of the S-allele is linked to an increased risk of anxiety and depression.
Conditions associated with the S-allele
The S-allele is commonly called the "grouchy" gene due to its association with unhappiness. Other studies have also linked the 5-HTTLPR short form to other conditions including:
- Anxiety related behaviour and stress response
- Antisocial behaviour
- Attention deficit disorder
- Psychological disorders such as autism, depression, bipolar disorder
- Addictive behaviour
- Sudden infant death syndrome
- Response to antidepressants
Response to antidepressants
The S-allele is associated with a decreased response to selective serotonin reuptake inhibitor (SSRI) antidepressants. SSRIs are commonly used as first-line treatment of depression. They act by blocking the action of the 5-HTT serotonin transporter. Commonly prescribed SSRIs include, fluoxetine (Prozac), paroxetine (Paxil, Paxil CR), citalopram (Celexa), sertraline (Zoloft), fluvoxamine (Luvox), and escitalopram oxalate (Lexapro).
People homozygous for the L-allele are more likely to respond well to SSRIs (within 3 – 4 weeks). People with the S-allele produce lower levels of the serotonin transporter targeted by SSRIs. This means people with the S-allele may have a delayed response to SSRIs and may require longer treatment period before any benefits are observed. Some people with the S-allele may not experience any noticeable benefits from SSRI medications, even after an extended treatment period.
Alternative antidepressants may be recommended for patients carrying the S-allele.
DNA testing for the S-allele
A simple DNA test can determine which form of the SLC6A4 gene a person has nherited. The test determines the length of the 5-HTTLPR in the SLC6A4 gene to distinguish between the S-allele and the L-allele.
People with two copies of the S-allele are more likely to be unhappy and will pass this form of the SLC6A4 gene to all of their children. People with two copies of the L-allele, have a decreased risk of unhappiness and depression. Heterozygotes have one copy of the L-allele and one copy of the S-allele. Having one copy of the S-allele also impacts the level of happiness. These individuals have a 50% chance of passing the S-allele to their children.