Overview

COGA, the Collaborative Studies on the Genetics of Alcoholism is the most comprehensive research project ever to be conducted on the inherited aspects of alcoholism.

Sponsored by the National Institute of Alcohol Abuse and Alcoholism (NIAAA) and the National Institute on Drug Abuse (NIDA), COGA is studying a large number of ethnically diverse families at eleven sites across the United States with the support of some of our country's most experienced researchers. Since 1991, COGA has interviewed more than 17,000 members of more than 2,200 families around the United States many of whom have been assessed several times.

The primary goal of COGA is to identify genes that increase or decrease the risk of alcoholism so that improved strategies for prevention and treatment of alcoholism can be designed.

Scientific Mission

There is a large body of twin and adoption-studies that demonstrate that about 30-50% of the risk for alcoholism is due to genetic factors. The primary goal of COGA is to identify the genes that increase or decrease the risk of alcoholism. Importantly, there is no one gene that leads or ‘causes’ alcoholism; rather, many different genes contribute in some measure to vulnerability. These genetic risk factors may act in different ways. Some genetic risk factors have already been identified, and have a direct effect on the rate at which alcohol (ethanol) is metabolized. These genetic risk factors typically decrease the likelihood that an individual will develop alcoholism. Other genetic risk factors may have a more indirect effect. For example, these genetic factors may affect an individual level of response to alcohol or a person's neuroelectrochemistry. Individual with certain psychiatric disorders, such as antisocial personality disorder or clinical depression, may be at increased risk for alcoholism. By pursuing different avenues that may contribute to the risk of alcoholism, COGA seeks to identify new genetic factors. We hope that this knowledge will lead to better approaches to prevent and treat this serious disease.

Study Design

COGA is a family study that has recruited indivduals and their families to participate in the search for genes and genetic variants that contribute to the risk of alcoholism. Since 1991, COGA has interviewed more than 17,000 members of more than 2,200 families from around the United States, many of whom have been longitudinally assessed. COGA developed the Semistructured Assessment for the Genetic of Alcoholism (SSAGA). Family members, including adults, children, and adolescents, have been carefully characterized across a variety of domains, including alcohol and other substance-related phenotypes, co-occurring disorders (e.g. depression), electrophysiology, key precursor behavioral phenotypes (e.g. conduct disorder), and environmental risk factors (e.g. stress). COGA participants have also provided a blood sample that has been used to create a repository of DNA and cell lines which are used for genetic studies. Confidentiality is important for this study and COGA has obtained a certificate of confidentiality from the NIH.

Scientific Resources

COGA has created a rich scientific resource of study data and biospecimens which can be used for current and future studies. To date, there have been over 400 publications reporting results from COGA data and samples. Data has been made available through a variety of resources.

Interview

COGA researchers will interview subjects using the SSAGA, or Semi-Structured Assessment for the Genetics of Alcoholism, specifically created for the COGA project. Each subject is asked to participate in the SSAGA, with different versions for adolescents and for parents being interviewed about their children. The SSAGA is a polydiagnostic psychiatric interview that will cover any drug or alcohol use as well as any emotional and/or medical problems the subject may have experienced. The SSAGA is designed to use diagnostic criterion from the DSM III-R, DSM IV, and ICD-10. The SSAGA has been translated into nine languages and has been used in over 275 studies. The wide adoption of the SSAGA ensures that data from COGA families are highly compatible with data from other studies and allows COGA to participate in numerous consortia that use meta-analytic methods to combine data and results.

Confidentiality

Subject's confidentiality is important to COGA. Subjects' names are never connected with the information they give. Rather, an ID number is assigned to them. COGA has also received the Confidentiality Certificate from the Department of Health and Human Services (DHHS) to protect researchers from being forced, even by court subpoena, to identify you.

Blood Sample

COGA requests that their subjects provide a blood sample, which is then processed and examined at Rutgers University. Genes not only carry information about eye and skin color, but also carry information about vulnerability to diseases, including susceptibility to alcoholism. This does not mean that any particular gene or genes will “make you an alcoholic” but rather that they can contribute in some measure to vulnerability. COGA is attempting to find those chromosomes involved in alcoholism and have located specific loci thought to be involved.

Brain Wave

The brain wave is called an event-related potential (ERP) and is similar to an EEG. Brainwaves are monitored in a non-invasive procedure that involves placing a cap on the subject's head, similar to a bathing cap. This cap will monitor the brain's natural electrical activity and will record the brain's response when the subject is presented with various stimuli. Subjects respond to computer programs on a screen in front of them that flash various stimuli on the screen.

After a significant event, or an important stimuli to which the subject is instructed to respond, there is an increase in electrical activity. COGA is investigating, for example, the P3 (or P300) peak of the ERP that occurs approximately 300 ms after the stimuli presentation. Varying amplitudes of the wave have different behavioral implications. The amplitude is fairly consistent throughout families and steady across time, suggesting an inherited component, as opposed to an environmental component.