Some therapists believe that there is a strong link between serious depression and psychosis.
When an individual suffers from psychosis, they will act as if they've lost touch with reality. This is usually the case with people who abuse drugs (either recreationally or otherwise). They will act in ways that suggest that they're 'not normal' and sometimes just 'snap' and lose it. People suffering from psychosis will not realise that they're not normal. In fact, everything they do is because of an imbalance in important neurotransmitters in the brain. They may report hallucinations, consistant delusional thoughts, personality fluctuations and severe disorderly thought processes.
Psychosis can stem from drug abuse, genetic predispositions, central nervous system conditions and diseases and brain damage. As well as imbalances within the brain's natural neurochemistry.
Major depressive disorders like MDD and Bi Polar sufferers usually report symptoms of severe depression. Meaning that they feel really down most of the time. They may have continuous thoughts of self-harm and suicide and will sometimes hurt themselves. Depression is a serious condition - if you or anyone you know is suffering from depression then please seek help. The sooner that you do; the better your chances are for eliminating these negative feelings and put yourself back on the right track.
The link between depression and psychosis symptoms is that the body will be neurochemically imbalanced. It's important to know that when our body's neurochemistry is out of balance, disease and mental conditions easily develop. There are natural ways to help with these conditions, without needing to resort to pharmaceutical drugs. I would advise the reader to check out some of the resources on this website (like binaural beat technology and mind machines) as these will help alleviate MDD depression and psychosis symptoms naturally.