Lack of Sleep

• A lack of sleep can cause a lack of focus. Many people who do not get enough sleep report feeling "foggy," having trouble with memory, and difficulty concentrating on work-related assignments. Sleep deprivation can cause mood swings which can lead to feelings of distraction. Lack of sleep can also be a risk factor for mood disorders. Symptoms for mood disorders include lack of focus.
  
  

ADHD

• ADHD, or attention deficit hyperactivity disorder, can affect children and adults -- although it is more prevalent in children and adolescents. Along with having a lack of focus and having trouble concentrating, people with ADHD can also have trouble with memory, organization, procrastination and feelings of boredom. As all of these symptoms contribute to difficulty with completing tasks, someone observing another with ADHD may feel that this person is having trouble focusing. In reality, there are a number of other symptoms that contribute to this appearance.
  
  

Depression

• Depression is a mood disorder that can cause lack of focus and other similar symptoms. People who have depression will usually have difficulty paying attention and making decisions, as well as feelings of restlessness. These all contribute to lack of focus. Depression can also cause someone to feel fatigued and disinterested in activities they used to enjoy, which can contribute to the appearance of being unfocused.
  
  

Poor Diet and Malnutrition

• High glucose diets can cause irritability, fatigue and a lack of focus. The Society for Neuroscience has also done studies that reveal that diets with high levels of saturated fats impair learning and memory. This can cause a lack of focus as well. Malnutrition is also a contributor to lack of focus. Malnutrition causes fatigue, which causes lack as focus, and also plays a role in the development of learning disabilities and other medical issues, such as neural problems in the brain and developmental delays, that can also contribute to a lack of focus.