A useful academic paper on the distinction between a personality disorder and a mental illness. Also very useful for an insight into psychiatric theory.

This paper is one of the most downloaded papers from the British Journal
of Psychiatry and they've made it open access.

Kendel, R. 2002, The distinction between personality disorder and mental
illness, British Journal of Psychiatry.
http://bjp.rcpsych.org/cgi/content/full/180/2/110

There's a lot of information about understanding the underlying concepts
of mental illness but its not an easy paper to read without having a bit
of background knowledge. It makes an attempt to define mental illness
and falls short as every other attempt with 4 definitions explained.
Mental illness clearly isn't a referent term in 2010.

There are some great bits of stigma within psychiatry in there and
examples of how psychiatry misunderstands the human condition.
"Certainly,^ it is commonplace for a diagnosis of personality disorder
to^ be used to justify a decision not to admit someone to a psychiatric^
ward, or even to accept them for treatment — a practice^ that
understandably puzzles and irritates the staff of accident^ and
emergency departments, general practitioners and probation officers, who
find themselves left to cope as best they can^ with extremely difficult,
frustrating people without any psychiatricassistance. The reasons for
this attitude were explored by^ Lewis & Appleby (1988 <#REF18>). Using
ratings of case vignettes^ by 240 experienced psychiatrists, they showed
that suicide attempts and other behaviours by patients previously
diagnosed as having^ personality disorders were commonly regarded as
manipulative^ and under voluntary control rather than the result of
illness,^ and that the patients themselves were generally regarded as^
irritating, attention-seeking, difficult to manage and unlikely^ to
comply with advice or treatment."

There's a useful precise definition of biomedical illness
"Scadding,^ a chest physician, defined a disease as 'the sum of the^
abnormal phenomena displayed by a group of living organisms^ in
association with a specified common characteristic or set^ of
characteristics by which they differ from the norm for the^ species in
such a way as to place them at a biological disadvantage'.^ He never
explained what he meant by biological disadvantage,^ but Kendell (1975
<#REF12>) and Bourse (1975 <#REF5>) both argued that it must at least
encompass reduced fertility and life expectancy."

There's a short snip that elucidates on why medicine would want to
medicalise personality disorders
"The evidence that personality disorders are harmful is quite^ strong
and not restricted to clinic populations. Drake &^ Vaillant (1985
<#REF9>), for example, compared 86 middle-aged men^ who met DSM—III
criteria for personality disorder with^ 283 men who did not. Both groups
had originally been members^ of a cohort of mainly working-class,
non-delinquent adolescent^ boys previously studied as a control
population in Boston by^ the Gluecks, so extensive background
information was available^ for all 369. Compared with the 283 men
without personality^ disorders, the 86 personality-disordered men (only
six of whom^ had disorders of antisocial type) had poor mental health
(79%^ /v/. 14%), poor occupational performance and job satisfaction,^
and poor social competence (58% /v/. 10%), and although alcohol^
dependence or misuse was partly responsible for their poor^ occupational
performance, it made little contribution to their^ poor mental health
and social competence."

One of the most interesting passages is on the influence of the
introduction of an effective treatmentin clinicians acceptance of a
social condition or behaviour as a medical illness.
"*The influence of effective therapies*
The second issue is the influence on medical attitudes of the^
acquisition of an apparently effective therapy. For nearly^ 150 years,
claims that alcoholism was a disease, from Thomas^ Trotter in 1804 to
Alcoholics Anonymous in the 1930s and 1940s,^ cut little ice with the
medical profession. It was only in^ the late 1940s and 1950s, when
disulfiram became available,^ that doctors changed their minds. Now, of
course, it is evident^ that disulfiram is not generally an effective
therapy, but^ in its early years enthusiastic reports of cures were
published^ in many different countries, and it was against this
background^ that the World Health Organization decided to include
alcoholism^ itself, as distinct from alcoholic psychoses and acute
alcohol poisoning, in the ICD, and medical organisations throughout^ the
world issued formal statements to the effect that alcoholism^ /was/ a
disease after all. The reasoning involved suggests an^ acceptance of the
socio-political definition described above,^ although this has rarely
commended itself to the medical profession.^ It does seem, none the
less, that possession of an apparently^ effective treatment can produce
a decisive change in medical opinion, and Campbell /et al/ (1979
<#REF6>) showed that an established^ medical role in diagnosis or
treatment has more influence on doctors' concepts of disease than on
those of the public. At^ present, neither personality disorder nor
obesity is accepted^ as a genuine illness by most British doctors; but
as effective^ drugs for treating obesity come into widespread use over
the^ next decade it is likely that obesity will come to be accepted^ as
a genuine metabolic disorder, and the same may happen to personality
disorders. Indeed, it is already happening to the 'borderline' disorders
as evidence accumulates that^ the disruptive and self-destructive
behaviours that characterise^ the disorder are amenable to forms of
psychotherapy (Linehan^ /et al/, 1991 <#REF20>; Bateman & Fonagy, 1999
<#REF3>). There is also some^ evidence that fluoxetine reduces
irritability and aggression^ in people with a variety of personality
disorders (Coccaro & Kavoussi, 1997 <#REF7>).^ If, therefore, the
psychiatrists andpoliticians who maintain that 'antisocial personality^
disorder' has as good a claim to being accepted as a^ mental disorder as
schizophrenia can demonstrate that it responds^ to some form of
treatment that is not simply a disciplined environment, it is likely
that the opposition will melt away,^ and the same will be true for other
types of personality disorder."