Breast growth begins during puberty and continues until age 18. Normal breast growth begins with the development of small tender breast buds, which usually appear by age 13. Hypomastia is the unusual condition in which breasts do not properly develop.
There is no medical research to substantiate the popular belief that wearing a bra while sleeping stunts breast growth.
Breast size is affected by many factors, including genetics, body weight and activity level. Hypomastia is often paired with other symptoms such as delayed menses.
Direct heat, radiation or other traumas to the breast bud during early puberty can stunt breast growth. According to a 2009 article by Doctors Jennifer E. Dietrich and Mary L. Brandt, chest damage from central line placement during chemotherapy or IVs can also affect breast growth.
Genetic disorders such as Ectodermal Dysphasia or Poland Syndrome sometimes cause stunted breast development. Hypomastia may also be associated with Crohn’s Colitis.
The drug Tamoxifen can stunt breast growth. Tamoxifen is usually used to treat breast cancer, but has also been tested by the National Institute of Mental Health to treat bipolar mania and Ormond’s disease.