Need a word for the inability to feel anger

I need a term for the inability to feel anger. Features desired:

1. Single word
2. Prefer connotations of incapacity rather than benefit
3. Prefer reasonably clear specificity to anger
4. More clinical tone slightly preferred over less clinical

To illustrate what I mean by #2 and #3, I considered serenity, but that word has positive connotations rather than connoting incapacity, and implies the absence of emotions besides anger (fear, for example).

Solution 1:

When one is unable to feel anger, and incapable of feeling any strong emotions, I would say that person is numb.

You can be numb with grief; unable to shed tears and to express your sorrow. You can be so stunned and be in shock that your whole mind and body is paralysed or frozen into a state of inactivity; this goes for emotions too.

In wikipedia I found this article: Emotional detachment

Emotional detachment, in psychology, can mean two different things. In the first meaning, it refers to an "inability to connect" with others emotionally, as well as a means of dealing with anxiety by preventing certain situations that trigger it; it is often described as "emotional numbing" or dissociation, depersonalization or in its chronic form depersonalization disorder.

Solution 2:

What about "non-irascible"?

i·ras·ci·ble : having or showing a tendency to be easily angered

from lat "ira", anger, wrath, rage

Solution 3:

I do not think there is a clinical term that is specific enough. Most will have strong psychiatric connotations. The only terms with clinical undertones that come to mind are inirritable, sedate and non-choleric or uncholeric.

Here are a few alternative suggestions:

unirascible

Wrathless

Unincensed

Unspleened, spleenless

Angerless

avirulent

stomachless, gall-less

The bold ones are negative in connotation in my opinion, and mean incapable of being roused to anger.

Solution 4:

You could also go for phlegmatic:

1. having a stolid or unemotional disposition
   
2. not easily excited

I would tend to use it for someone who is excessively calm and, to me, it carries slightly negative connotations.