Professional advice in pamphlets suggests not to make major life decisions without consultation. Does that mean depression makes your mind vulnerable as if "not running on all cylinders?" Research indicates that vulnerability could be due to imbalances in the brain neurotransmitters serotonin and norepinephrine. Deficiency in the first may cause sleep problems, irritability and anxiety. The same in the second may contribute to fatigue and depressed mood. What's interesting is that when you read labels on memory enhancement supplements some ingredients are supposed to build up transmitters which cause brain cells to communicate with one another.
This communication takes place within the neuron or nerve cell. It takes place when an electrical pulse is transmitted along the cell's axon connected to another neuron. There are neurotransmitters stored in small vesicles which get released by the electric current into the synaptic gap between two neurons which activates the adjacent cell. These molecules are then either destroyed by enzymes or reabsorbed into the neuron. But there is an antidepressant called SSRI which stands for Selective Serotonin Reuptake Inhibitor. This antidepressant postpones the neurotransmitter's recycling so it can operate longer.