Having a mental disorder doesn't give you a free pass, but realizing it can help you deal with it.  For example, your alcoholic in-law: being alcoholic doesn't give him a free pass for all the harm he's done, but realizing he's alcoholic could lead him to treatment and abstinence.  If he doesn't want to be treated for his illness, then he doesn't deserve any sympathy for the problems it causes, especially those it causes for others.

My  mother-in-law is badly depressed, but instead of seeking help, she sits in the dark living room and does the absolute minimum to maintain her life, while complaining about how bad it is, and blaming her husband for it (he had a stroke that gave him aphasia about four years ago, and recently, had his leg amputated).  When he first had his stroke, she refused to go to counseling.  She won't talk to her doctor about it because if she does, that means she's crazy.  Instead, she insists there's nothing wrong with her while scratching open sores into her legs and shoulders, which she insists are due to bird mites which bite no one else (her husband enjoys watching the birds at a feeder outside the house, so that is his fault as well).

We spend most of our free time at their house, maintaining it so that they have a decent life, and the more time we spend with her, the better she gets.  But if she'd recognize that she has a problem and deal with it, she and everyone around her would be a lot happier.  I sympathize with her plight, having suffered from depression myself, but I also continue to tell her that she is not bad off, and that she needs to deal with her mood in a practical way.  A large part of my motivation is protecting her husband and her daughter from her.

If someone has a compulsive shopping habit, they need to recognize it and take responsibility for it by dealing with it, not by asking for their debts to be forgiven.  The people around them need to take responsibility and recognize it as well, and not act as enablers.

Conceptualizing the problem as one of character failure and lack of will is usually very satisfying for outside observers, but is rarely helpful to those who actually have to deal with it, both the sufferer and those with emotional attachments to them.

That is very sad, that your mother-in-law has such a terrible life and that you and your wife also suffer as a result.  She is a good example of a person who really is mentally ill, not merely irresponsible or using mental illness as an excuse for bad behavior, and she should be under psychiatric care; it is likely that the right psychiatric medication could help her a great deal.  But of course, the trick is getting her to seek help (although it might also be possible to have her committed).

The reality is that she isn't bad off enough to be committed.  She still does the minimum necessary to maintain her life, and she's merely miserable.

Lately she's been showing some signs of progress.  I hope it isn't a false start.

But it illustrates the problem of "man up and take responsibility" as a solution.  If I blamed her, things would be a lot worse.  Instead, I have a lot of patience and sympathy for her, even when she's utterly foul.

I agree that your situation with your mother-in-law is a good example of how some people really do need help, they can't just be told to straighten up and fly right.  I also think that given your observation that she injures herself in the false belief that she is infested with bird mites, she has crossed the line from being merely depressed to actually insane, and could be committed to a mental institution.  The legal definition of insanity is, being dangerous to oneself or others, and your mother-in-law seems to fit that definition.  But if you can help her yourself, that may be the better approach.

"Maybe.  I suppose I should be more sympathetic, but I've experienced a lot of people in my life who seem to use mental disorders as some kind of excuse or cop-out."

I don't consider it a mental disorder, but the internet and a credit card have made it too easy to get in trouble.  I have to stay away from eBay, because I often find something that I needed like another hole in my head, and have often been ripped off on shipping charges.  Having a PayPal account makes it all too easy.

Amazon made it even easier to spend too much, with their "one-click" purchasing.

I've gotten some great things from many vendors, but I have to watch myself, but do I consider it a mental illness?  No, I don't.  I just have to exhibit a little self-restraint.  When you get a >$1K credit card bill for the stuff you've purchased, it's a kick in the butt.  

there's only one way to find out...

I see nothing wrong with having a lot of food in stock, provided that you do eventually eat it.  If you are buying so much food that you will never eat all of it, and some significant portion of it will eventually become too old to be safely edible and will be thrown out, then you are overdoing the food shopping.  I would also say that your former girlfriend who used to buy shoes that she would usually return the next day, does have a shopping problem.  While it can be therapeutic to go shopping, even then you should be shopping for something that you actually need and want, not something that you will probably return.  Otherwise you are just wasting the time of both yourself and the retail clerks involved.  And if there is absolutely nothing that you actually need, then don't go shopping.  There are lots of other things we can do to raise our spirits.

Skeptic,

"I see nothing wrong with having a lot of food in stock, provided that you do eventually eat it. "

You don't know me very well.  I'm a retired microbiologist.  Almost nothing here goes to waste, unless I fuck up in the kitchen like I did last week.  I tried making oven-baked potato chips using redskin potatoes and olive oil.  They were terrible, and most got fed to the garbage disposal.  Perhaps a long soak in some acidulated-water would have helped.  Maybe next time.

Much of the food I have on hand at the moment is

1).  Fresh from the garden
2).  Canned
3).  Dried
4).  US Army MREs.
5).  Frozen

Canning I've done for many years.  Dried foods I got used to from backpacking.  MREs I was introduced to by a friend in the Army, and I happen to like them (sometimes they need some hot sauce).  Occasionally, I'll splurge and get some carry-out Chinese food, but I can get 5 meals out of that for $6.  

BTW, when I go hunting, I only hunt and shoot what I can eat.  I'd like to have another hassenpfeffer.

Tonight's snack is going to be the leftover chow mein noodles that I got with the last carry-out order.

No, very little food here goes to waste.  

there's only one way to find out...

Since there are many possible types of emergencies which can cause temporary or even prolonged food shortages or disruptions in existing routes of food distribution, there is something to be said for having lots of food in storage at one's home.  There is also the advantage that it gives you a large range of possible meals that you can prepare without having to go out for more shopping.  You can indulge your dietary whims at any given time.  And since the food is not going to go to waste, then I would have to conclude that despite your tendency to buy and store large quantities of food, this is not a form of shopaholism.