In this edition of UCL’s special test service we are providing information about a genetic test for the serotonin transporter gene (5-HTT) and its clinical significance.
The test detects two types of alleles, the shorter allele (S) and the longer allele (L or XL), in the 5-HTT gene-linked polymorphic region (5HTTLPR). Research suggests that individuals with the SS genotype (shorter allele) are more susceptible to stress-related conditions such as depression, alcohol addiction, and suicidal behavior. The test aims to determine an individual’s genetic predisposition to stress and depression, allowing for early prevention and treatment.
Specimen Collection: Whole Blood (EDTA) 2 mL, at least 1 mL required, can be stored at 4℃ for 2 weeks Specimen Rejection: Non-EDTA tube collection, specimen clotting or less than 1 mL Turnaround Time: 7 working days Analysis Method: PCR (Polymerase Chain Reaction) Reference Range: Detection of genotypes includes SS, LL, SL, SXL, LXL (five types)
Report Interpretation:
- Target gene: 5-HTT gene-linked polymorphic region
- Report Form:
• Shorter Allele (S): Lower stress resistance
• Longer Allele (L or XL): Provides stronger stress resistance
Clinical Significance:
Serotonin is an important neurotransmitter in the brain that regulates various functions such as sleep-wake cycles, appetite, hormone secretion, aggression, body temperature, emotional cognition, and stress response. The serotonin transporter gene (5-HTT) located on chromosome 17 in humans encodes a protein responsible for regulating serotonin transport, recycling released serotonin back into the secreting cells, thereby modulating serotonin levels. Research suggests that the 5-HTT gene is one of the crucial factors determining an individual’s susceptibility to stress-related disorders like depression.
The 5-HTT gene has two major allelic variants in the promoter region (5HTTLPR: 5-HTT gene-linked polymorphic region): a shorter variant (S) and a longer variant (L or XL). Studies have shown that individuals with the shorter allele (S) are associated with being “easily overwhelmed by life’s continuous stresses,” whereas those with the longer allele (L or XL) exhibit stronger stress resistance. Therefore, the SS genotype represents lower stress resistance, and research has linked it to depression, alcohol addiction, and suicidal behavior.
Depression is caused by multiple factors, including genetic, psychological, and environmental influences. Although the 5-HTTLPR genotype is not the sole cause of depression, it has been proven to affect an individual’s resilience to adversity. Additionally, the 5-HTTLPR genotype can influence the efficacy and side effects of certain antidepressant medications. Depression is a treatable condition, and therefore, early prevention and treatment based on understanding one’s own genetic profile through 5-HTTLPR genetic testing is considered the optimal approach for preventing and managing depression.
Testing Facility: Union Clinical Laboratory at Taipei HQ
Important Note: Laboratory Developed Test using the methods validated by this laboratory.