Bipolar I is the most extreme case of bipolar disorder. Bipolar I mood swings are more difficult and serious and, in the case of the manic phase, dangerous. Bipolar I can cause serious implications for work or school. Bipolar II is less severe, bringing about changes in mood but not causing major disruptions in normal, every day life. Cyclothymia is the least severe of the bipolar family, the depression and mania can be disruptive, but they are not as severe as they are in the other two bipolar types (Grieco & Edwards, 2010). A person can develop bipolar disorder as a result of an imbalance of neurotransmitters or hormones. Neurotransmitters play a big role in the production of moods in a person; an imbalance of neurotransmitters can disrupt the organization of moods. The same holds true for an imbalance of hormones, which also play a part in moods. Other causes of the disorder include inheriting the disorder from a family member. The genes that pass on bipolar disorder have yet to be found by scientists, but it is more common for a person to develop bipolar disorder if a blood relative also has the disorder. Finally, the environment of the individual can cause the person to develop bipolar disorder.