Mesandy
08-09-2007, 08:32 PM
A Gene Study
Whether anxiety disorders are physiological or psychological conditions has been debated in forums from Usenet newsgroups to medical journals. A study found in the June 14, 2000 Journal of Abnormal Psychology demonstrates that the answer may be "both."
The Gene
The gene investigated in the study is 5-HTT, a serotonin transporter gene. Serotonin is a neurotransmitter, a brain chemical which helps transmit messages. Researchers have discovered a variation in 5-HTT that is linked to increased regulation of serotonin levels. When serotonin regulation is increased, neurons use the serotonin more quickly, leaving less of it available in the brain. Other researchers have theorized that the decreased availability of serotonin may be linked to anxiety disorders, depression, and other psychiatric conditions.
In the new study, researchers found that people with the variation in 5-HTT demonstrated a greater fear response during the experiment.
The Participants
The researchers chose 72 participants for the study. Blood samples were analyzed to determine which variation of 5-HTT each participant had. The variations of the gene are described as the "long" form (the one which increases serotonin regulation) and the "short" form. Participants with the long form of the gene had not experienced symptoms of anxiety disorders or been diagnosed with anxiety disorders in the past. Prior to the experiment, participants filled out the Anxiety Sensivity Index (ASI), a self-test which is intended to measure the fear caused by certain sensations in the body, such as shortness of breath or heart palpitations.
The Experiment
All participants went through the same experimental process. Each took two breaths of pressurized air, spaced 10 minutes apart, through a mouthpiece. The first breath was of pressurized room air, and the second was of a carbon dioxide-oxygen mix. The mix was used to cause participants to feel short of breath. The shortness of breath sensation can lead to anxiety symptoms in some people.
The Results
Participants with the long variation of 5-HTT experienced increased anxiety when they took the second, CO2-mix breath. Paricipants with the short variation did not. Additionally, participants who had the long variation along with a high level of anxiety sensitivity (measured with the ASI) also demonstrated less heart rate variability during the experiement. Less variability means that the heart rate increased during the experiment and remained the same afterwards. Participants with the long variation and low anxiety sensivity as well as participants with the short variation of the gene demonstrated normal heart rate variability.
The Conclusions
Researchers formed some basic conclusions based on the results of the experiment:
Participants with the long form of 5-HTT appear to have a higher risk for experiencing anxiety symptoms when in fearful situations, as shown when they reacted with higher anxiety when experiencing shortness of breath.
Participants with the long form of 5-HTT along with higher anxiety sensitivity may have a higher risk for maintaining anxiety symptoms even after a fearful situation has ended. Their risk was demonstrated by less heart rate variability during the experiment.
Physiological (5-HTT variation) and psychological (anxiety sensitivity) factors combine for a higher risk in the development of anxiety symptoms during threatening situations (or situations perceived as threatening).
While the 5-HTT variation appears to play a role in the development of anxiety symptoms, other genes are being studied, as researchers believe more than one gene is responsible for the development of anxiety disorders.
Reference: Schmidt NB, Storey J, Greenberg BD, Santiago HT, Li Q, Murphy DL (2000). Evaluating gene x psychological risk factor effects in the pathogenesis of anxiety: a new model approach. J Abnorm Psychol 109(2):308-20.
thanks,
mesandy:) .
Whether anxiety disorders are physiological or psychological conditions has been debated in forums from Usenet newsgroups to medical journals. A study found in the June 14, 2000 Journal of Abnormal Psychology demonstrates that the answer may be "both."
The Gene
The gene investigated in the study is 5-HTT, a serotonin transporter gene. Serotonin is a neurotransmitter, a brain chemical which helps transmit messages. Researchers have discovered a variation in 5-HTT that is linked to increased regulation of serotonin levels. When serotonin regulation is increased, neurons use the serotonin more quickly, leaving less of it available in the brain. Other researchers have theorized that the decreased availability of serotonin may be linked to anxiety disorders, depression, and other psychiatric conditions.
In the new study, researchers found that people with the variation in 5-HTT demonstrated a greater fear response during the experiment.
The Participants
The researchers chose 72 participants for the study. Blood samples were analyzed to determine which variation of 5-HTT each participant had. The variations of the gene are described as the "long" form (the one which increases serotonin regulation) and the "short" form. Participants with the long form of the gene had not experienced symptoms of anxiety disorders or been diagnosed with anxiety disorders in the past. Prior to the experiment, participants filled out the Anxiety Sensivity Index (ASI), a self-test which is intended to measure the fear caused by certain sensations in the body, such as shortness of breath or heart palpitations.
The Experiment
All participants went through the same experimental process. Each took two breaths of pressurized air, spaced 10 minutes apart, through a mouthpiece. The first breath was of pressurized room air, and the second was of a carbon dioxide-oxygen mix. The mix was used to cause participants to feel short of breath. The shortness of breath sensation can lead to anxiety symptoms in some people.
The Results
Participants with the long variation of 5-HTT experienced increased anxiety when they took the second, CO2-mix breath. Paricipants with the short variation did not. Additionally, participants who had the long variation along with a high level of anxiety sensitivity (measured with the ASI) also demonstrated less heart rate variability during the experiement. Less variability means that the heart rate increased during the experiment and remained the same afterwards. Participants with the long variation and low anxiety sensivity as well as participants with the short variation of the gene demonstrated normal heart rate variability.
The Conclusions
Researchers formed some basic conclusions based on the results of the experiment:
Participants with the long form of 5-HTT appear to have a higher risk for experiencing anxiety symptoms when in fearful situations, as shown when they reacted with higher anxiety when experiencing shortness of breath.
Participants with the long form of 5-HTT along with higher anxiety sensitivity may have a higher risk for maintaining anxiety symptoms even after a fearful situation has ended. Their risk was demonstrated by less heart rate variability during the experiment.
Physiological (5-HTT variation) and psychological (anxiety sensitivity) factors combine for a higher risk in the development of anxiety symptoms during threatening situations (or situations perceived as threatening).
While the 5-HTT variation appears to play a role in the development of anxiety symptoms, other genes are being studied, as researchers believe more than one gene is responsible for the development of anxiety disorders.
Reference: Schmidt NB, Storey J, Greenberg BD, Santiago HT, Li Q, Murphy DL (2000). Evaluating gene x psychological risk factor effects in the pathogenesis of anxiety: a new model approach. J Abnorm Psychol 109(2):308-20.
thanks,
mesandy:) .