Will you please let me know the difference between...

Major depressive disorder
It's characterised with the following symptoms with progressive course not in attacks  (episodes) such as in Bipolar disorder
Symptoms
sadness, hopelessness, worthlessness, or an empty feeling
pessimism
guilt
a lack of interest in things you used to enjoy
insomnia or sleeping too much
restlessness or a lack of concentration
irritability
eating too much or too little
headaches, or various other aches and pains
thoughts of death or suicide, or suicide attempts
Bipolar disorder 

If you have bipolar disorder, you may alternate between depression and hypomania or mania. You may also have periods in between when you have no symptoms
Mania and Hypomania symptoms

restlessness, high energy, or increased activity
racing thoughts or being easily distracted
grandiose ideas or unrealistic beliefs
euphoria
irritability, aggressiveness, or being quick to anger
needing little sleep
a high sex drive
Severe mania can cause delusions and hallucinations
Treatment
In treating depression we usually start with antidepressant such as Prozac but in Bipolar disorder we usually use mood stabilizer such as Lithum along side other drugs such as antidepressants
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