Chemical "locha"!!!!!!

This term was first used in the movie Lage Raho Munnabhai and I had always wondered about it but never found the time to read it up and understand what happpens inside of our brains and how the chemical locha happens.
but recently I was looking for an explanation and found one which is quite interesting and easy to understand without much medical jargon.

Depression and depressive illnesses are classified as mood disorders in the medical field, including everything from Major Depression to Dysthymia. They have a number of symptoms that affect people socially, occupationally, educationally, interpersonally, etc. How does one become depressed? Basically, here's how it works: the nerves in our brain don't touch each other, but rather pass messages from one to the next through chemicals called neurotransmitters. We need just the right amount of this chemical between the nerves to pass the exact same message to the next nerve. If there isn’t enough of that chemical, the message doesn't get passed along correctly and in this case, depression or a depressive illness can result. When it comes to depressive disorders the chemicals most frequently out of balance are serotonin and norepinephrine.
A person living with depression does not always have the same thoughts as a healthy person. This chemical imbalance can lead to the person not understanding the options available to help them relieve their suffering. Many people who suffer from depression report feeling as though they've lost the ability to imagine a happy future, or remember a happy past. Often they don't realize they're suffering from a treatable illness, and seeking help may not even enter their mind. Emotions and even physical pain can become unbearable. They don't want to die, but it's the only way they feel their pain will end. It is a truly irrational choice. Suffering from depression is involuntary, just like cancer or diabetes, but it is a treatable illness that can be managed
( TAKEN FROM SAVE.ORG)