2.1. Opioid Addiction

Opioid addiction

2.2. WAGR Syndrome

The BDNF gene is located in a region of chromosome 11 that is often deleted in a condition known as WAGRO syndrome. This condition is a variant of WAGR syndrome, which is a disorder that affects many body systems and is named for its main features: a childhood kidney cancer known as Wilms tumor, an eye problem called anirida, genitourinary anomalies, and intellectual disability (formerly referred to as mental retardation). WAGRO syndrome also includes obesity. The deletions that cause WAGRO syndrome remove many genes from one copy of chromosome 11, including part or all of the BDNF gene. The loss of this gene is responsible for weight gain that begins in childhood in people with WAGRO syndrome.

People with WAGRO syndrome may be at greater risk of neurological problems such as intellectual disability and a developmental disorder called autism spectrum disorder that affects communication and social interaction than those with WAGR syndrome. It is unclear whether this increased risk is due to the loss of the BDNF gene or other nearby genes.

2.3. Other Disorders

Certain common genetic variations (polymorphisms) in the BDNF gene have been associated with an increased risk of developing psychiatric disorders such as bipolar disorder, anxiety, and eating disorders.

Most studies have focused on the effects of a particular polymorphism in the BDNF gene. This variation alters a single protein building block (amino acid) in the protein, replacing the amino acid valine with the amino acid methionine at position 66 (written at Val66Met or V66M). This change impairs the protein's ability to function. Many studies report an association between the Val66Met polymorphism and psychiatric disorders; however, some studies have not supported these findings. It is unclear how changes in the BDNF gene are related to these disorders. A large number of genetic and environmental factors, most of which remain unknown, likely determine the risk of developing these complex conditions.