The exact cause of global developmental delay (GDD) is not always clear, and it may vary depending on the individual. In some cases, GDD may be due to genetic factors, exposure to toxins, or complications during pregnancy or childbirth. In other cases, the cause of GDD may be unknown.

Some possible causes of GDD include:

1. Genetic factors: Certain genetic conditions, such as chromosomal abnormalities or genetic syndromes, can cause delays in multiple areas of development.
2. Exposure to toxins: Exposure to certain toxins, such as lead or alcohol, during pregnancy or early childhood can interfere with a child's development.
3. Complications during pregnancy or childbirth: Complications such as premature birth, low birth weight, or lack of oxygen can affect a child's development.
4. Infections: Some infections, such as meningitis or HIV, can cause delays in development.
5. Other medical conditions: Certain medical conditions, such as cerebral palsy or epilepsy, can cause delays in development.

It's important to note that the causes of GDD are not always known, and more research is needed to fully understand this condition. If you are concerned about your child's development, it's important to speak with a healthcare provider or educational specialist to determine the best course of action.