12 months weed free but just depressed.

So I have just hit the 12 months mark weed free and whilst all the side effects such as cravings, insomnia and all the standards effects you feel to start off with have gone completely. I just feel depressed and have little enthusiasm for anything. I try to think of things that once excited me and just don't feel it anymore. I never felt this way before or during my weed habit. Could this really be something to do with my quitting even 12 months on?

Edit: A big one are these intense feels of guilt and shame for mistakes as far back as when I was a child that I just can't shake. In the past I could view them and think 'well I was young and stupid no biggie' where as now I just fixate and ruminate on them.

Congratulations on being able to stay clean for a year. Once I had one year under my belt, I knew that there was no magical holiday that would make me pick up a drink or drug.
It is one day at a time.
Are you making any 12-step NA, EA or AA meetings or getting any counseling? Putting down the drug allows us to work on other problems with a clear mind. Recovery is repairing the damage and scars left by our use.
Just quitting the drug or alcohol doesn't automatically make things better. One has to fill the hole left behind, hopefully without another addiction, but we can be compulsive people.
Is it possible that your depression isn't related to the absence of weed? When was your last thorough physical exam?
Chemical imbalances like thyroid, etc. can cause depression and is treatable. A professional evaluation may uncover the need to do some work on yourself.
There is no shame in asking for help when you need it. On the contrary, asking for help is a sign of strength that same people just can't bring themselves to do, either through ego, shame or self-esteem issues.
In rehab we called it 'surrender to win'.
Best of luck to you.

I remember getting off weed.
People claim it's not physically addictive, but the first 3-4 months, I couldn't sleep, couldn't eat, and I justy felt... Surreal all the time.
But it's more than that.
You don't just become addicted to the substance, but also to the RITUAL.
Shredding weed, rolling up, sharing the joint, etc.
While you were smoking, you had all that to occupy your time, so now it may feel empty.
My advice: 'get a hobby, or even better: get some volunteer work (read to children in hospitals, care for the elderly, whatever)
It will replace the emptiness with a feeling of accomplishment.

Have you ever thought of working out, playing a sport, like hackey sack or racquetball, kicking the soccer ball, badminton, stuff like that? Something to get you outdoors or away somewhere close by without going back to an old routine of what you're accomplishing already being 12 months free. Good Job by the way!!!!!! Just do something where you get away and maybe that might help with some of the depression, you may need to change your environment up to not be so depressed. New friends, new places, stuff like that.