Thanks for your question.
The usual dose range of Lamotrigine is from 100 to 200 mg per day and the maximum dose is generally 200 mg per day for Bipolar disorders.
Some doctor may use the higher doses provided the patient is able to tolerate it because increasing the dose may lead to increase in side effects.
The best parameters for finding the appropriate doses are the clinical response (patient is free of symptoms) and nil or minimal side effects at that particular dose.
In my personal experience, lowest possible dose should be used in patients to minimize the side effects.
Because of your gentle prompt I went to the manufacturer's dosage guidelines and they cofirmed your statements.. Two weeks back I shifted lamotrigine from a nightly dose to a morning one after learning that it had lifting element to it. The result was that my sleep became deeper and longer by nearly two hours.. Could you confirm or refute if this was due to the shift?
With Lamotrigine, sedation is not a common side effect although it may be experience by some patients. In other words, it is not considered to be a sedating mood stabilizer.
May be, you also did not find it sedating but probably a bit activating and hence noticed a improvement in your sleep duration once you start taking it in morning.