Is Lead Poisoning Causing Some Cases of LD, ADD & ADHD?

Recently, there have been many recalls of children's products because of the discovery of unsafe amounts of lead. These prompted some internet research on my part. I had a head start, armed with the knowledge of many symptoms caused by lead from previous research.

However, I wanted to re-check exactly what symptoms lead produced, as well as see if there were more symptoms I hadn't known about. I then wanted to compare the symptoms and effects to certain learning and behavioral conditions affecting children (LD, ADD, and ADHD ) to see if there was a connection between those and lead poisoning.

Symptoms of Lead Poising, or Plumbism
Firstly, you need to know that some lead poisoning can cause emergency symptoms, such as abdominal pain and/or cramping, vomiting, seizures, staggering or stumbling, muscle weakness, and coma.

However, it is more common for lead poisoning to build up over time and do internal nerve, kidney, and brain damage with either no symptoms or the following symptoms.

Lowered IQ, difficulty sleeping, slowed growth, hearing problems, behavior problems, attention/focus problems, failures at school, kidney damage, irritability, aggressiveness/aggressive behavior, low or reduced appetite, low or reduced energy, headaches, reduced sensations, loss of developmental skills (mainly in younger children), anemia, and constipation are all symptoms of lead poisoning.

Some Conditions That Have Similar Symptoms
Is it possible that in some of the cases of Learning Disabilities (LD), ADD, or ADHD, children might have had early or prolonged exposure to lead? If so was that causing these disorders?

Take a look at the symptoms that are shared with these problems.

The shared symptoms are low IQ, behavior problems, attention/focus problems, difficulty sleeping, irritability, failures at school, and aggressiveness.

Not all children will have all of the symptoms for either Plumbism or any of the other conditions mentioned. Some may have only one.