Speakng as someone who has suffered with depression for four years, not to the extent where I required any hospitalisation but who was on a relatively high dose of Sertraline of 150mg daily I can say the following:
(A) I had good days and bad days, my mood at night time gave no indication of how I'd wake in the morning.
(B) On bad days rationality could be difficult - not wanting to go out, open mail or answer the phone.
(C) For the majority of the time you could not tell I was suffering at all - I could laugh and joke with friends just like normal.
(D) I wouldn't wish depression on my worst enemy - it is so hard to understand, a lot of people find it really difficult to talk about and it is really difficult to tell a point in time when you are fully better.
I'd been through a tough time, I'd lost two close relatives in quick succession, my marriage of 10 years had broken down, I had the associated money issues setting up a new home brings and I was made redundant from work. All these events happened over a space of 3 years but it ended up being enough to chip away at me and take me through breaking point.
In my case my breaking point manifested itself in me waking up tearful for no apparent new reason, I also had a feeling of low personal worth.
I was used to being the life and soul of the party, confident and successful in a high pressure, highly regulated customer-facing role and braking in tears felt very alien to me so I sought help.
I did various questionnaires, kept a log of daily happenings and the effect +ve or -ve on me - I was utterly shocked that the scores I achieved in the questionnaires and consultation labeled me as severely depressed.
I've done my best here to give a brief insight in to my depression for those forum members who have been fortunate enough not to suffered a similar illness or condition.
Andreas Lubitz (if not physically incapacitated), in his opinion, felt his life was no longer worth living. If he was in such a bad state of mind his capacity to think rationally would have been severely depleted - even to the extent he probably hardly gave all those poor victims a second thought. Clearly the captain of the flight felt it safe to leave the people's safety in the hands of Mr Lubitz, so his state of mind was convincingly masked.
I believe, going forward, the two PEOPLE in the cockpit at any one time is the best response to this terrible tragedy.
Without, for one second, forgetting the horror and sadness for those left behind following the loss of their loved ones, we need to put things in to context when seeking to try and ensure that this doesn't happen again.
According to the Aviation Safety Network there have been 8 cases of pilot suicide in the last 41 years and with between 90-100,000 flights taking place each and every day the probability of being killed as a result of pilot suicide is truly miniscule.
Any potential solution has its own flaws. The cockpit door locks since 9/11 was the right thing to do to stop undesirables getting in. In a hijacking it's a great solution because it cannot be overridden from the cabin, however, in this instance the best solution for one instance became the worst.
I hope this post comes across in the right manner.
My heart goes out to all people who have suffered a loss in this horrible crash and nothing.