The document describes the design of an expert system for diagnosing depression. It begins by providing background on depression and expert systems. It then outlines the components of the proposed depression diagnosis expert system, including the knowledge base, inference engine, user interface, and variables/symptoms used. The document concludes by noting that designing such a system is challenging and requires extensive medical knowledge, but that expert systems have potential to assist doctors in making accurate diagnoses. The system uses patients' answers to questions about symptoms to determine the type and severity of depression.

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About a decade ago, it was thought to be a challenge to develop such an expert system which
will assist doctors and those working in medical field to help diagnose a patient’s disease
correctly. However, thanks to recent day advancement in technology this has been made
possible by scientists who have developed such systems. In the beginning, Artificial
intelligence was considered to be used only for military based operations but nowadays it is
being widely used in all sorts of applications. This has been made possible by the use of
computers that think and learn by themselves in order to provide assistance to the doctors to
diagnose a patient’s disease correctly. Although these systems are still in testing phase and
are only limited to one particular disease, this can be overcome with more research and
passage of time. This research paper shows an expert system for diagnosing the disease of
depression.

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Depressive disorders have been with mankind since the beginning of recorded history.
[1] [2]
Hippocrates referred to depression as melancholia . Depression, also referred to as
clinical depression, has been portrayed in literature for hundreds of years, but what do we
mean today when we refer to a depressive disorder? Most people when asked what
depression is think that it’s when someone is so sad that they feel worthless and constantly
think about taking their own lives. What they don’t know is that it’s much more than that.
Even though depression has been recognized as a clinical syndrome for over 2000 years but
still no proper definition of this disease can be found because it varies from person to person
but in general you can define it as “ a mental state characterized by a pessimistic sense of
inadequacy and a despondent lack of activity which reflects a sad and/or irritable mood
exceeding normal sadness or grief” [3]. According to the World Health Organization, there are
approximately 450 million people in this world who struggle with mental health problems. [4]
Artificial intelligence, which was considered to be a fairy tale, has really evolved during the
last decade. The world ‘s first commercial application of AI was IBM’s DEEP BLUE ,a super
computer which played against the world chess champion Garry Kasparov and in this match
Deep Blue won proving that AI can help mankind in a lot of ways to help improve our
society. In this research paper, we will try to design an expert system to diagnose and purpose
medication/ treatment for patients suffering from depression, but again question arises what
exactly an expert system is, this is described in detail in section below.
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The definition of expert system varies. Some definitions are based on structure and some are
based on both structural and functional components. But based on functionality you can
define an expert system as “An expert system is a computer program that simulates the
judgement and behaviour of a human or an organization that has expert knowledge and
experience in a particular field” [5] and is used to execute complex tasks for these reasons
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The working model of an expert system is shown below with explanation of each component:
1. Knowledge base consists of problem-solving rules, procedures, and intrinsic data
relevant to the problem domain.[5]

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2. Data acquisition is the external data acquisition system gives the input for the
definite application. In these data must be collected or entered by hand or automated
like remote sensing.[5]
3. Inference engine is a generic control mechanism that applies to axiomatic knowledge
in the knowledge base to the task specific date to achieve the solution.[5]
4. External interfaces help of this program the system replaces data and information
like computer stimulation modules.[5]
5. User interface means the components through which the user communicates and
produces reports.[5]
6. Domain expert are group or the individual expertise whose knowledge is used in
expert system.[5]
7. Knowledge user is group or the individual who is taking the benefit from expert
system.[5]
8. Knowledge engineer is a person who has skill or learner in the design, development,
implementation and maintenance of expert system.[5]
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Depression is divided into two types, endogenous and neurotic. Endogenous means
that the depression comes from within the body, perhaps of genetic origin, or comes
out of nowhere. Neurotic or reactive depression has a clear environmental
precipitating factor, such as the death of a spouse, or other significant loss, such as the
loss of a job. The disease of depression can cause serious problems with the increased
chances of HIV, asthma and many other major medical illnesses, furthermore it can
increase the morbidity (illness/negative health effects) and mortality (death) from
these and many other medical conditions. There are three major types of depression
disorder i.e.
• Major depression: it is characterized by a combination of symptoms that last
for at least two weeks causing sadness, irritable mood. This is the most serious
type of depression in which a patient can commit suicide.

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• Dysthymia: this type of depression is less severe but more long lasting leaving
drastic effects on the patient.
• Bipolar disorder/manic depression: this type of disorder carries symptom
from both above mentioned disorders.
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The expert system of depression diagnosis has selected to use data simulation which
will be predefined and later the system will fetch data from patients. The search
policy begins with the facts and rules that are relevant to the facts to find new facts
which then guide us towards our final goal.
In this expert system, data fetching begins within the system when a patient comes up
and presents different symptom such as headaches, sleeplessness, hopelessness,
feeling of guilt etc. These rules are objects that are applied to find correct diagnosis
through the knowledge structure to find out what type of depression disease the
patient have.
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Our goal is to design depression expert system in such a way which will diagnose the
patients disease properly, following are the questions which are asked/inputted by the
user or patient about the symptoms and actual behaviour of the patient to distinguish
the exact type of depression.
The following questions will be asked while developing depression expert system to
establish the rules:
1. Age of patient
2. Sex of the patient
3. Have you ever been treated or hospitalized for depression?
4. Have you ever seek out help of a psychiatric or mental health worker?
5. Do you suffer or ever suffered from any serious disease i.e. stroke, heart/kidney/liver
failure?

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6. Do you have any of these symptoms i.e. shortness of breath, dizziness, panic attacks
or unexplained symptoms?
7. Do you have sleeping problems?
8. Have you ever felt sadness, miserable, hopeless, worthlessness, guilty?
9. Do you have an appetite problem?
10. Do you have recurring thoughts of dying, death or suicide?
11. Do you unusually feel tired or feel that you have lost all of your energy?
12. Have you experienced any of these:
a. Loss of loved one?
b. Divorce or separation?
c. Financial problems?
d. Other personal problems?
13. Do you think you are depressed?
14. Do you have any drug problem i.e. alcohol/drugs?
15. Do you find it difficult to get yourself involved into pleasure full activities?
The quires which would be used by the expert system are as follows:
Check_ Patient_ history Check whether patient had any
previous depression history
Check_ Patient_ Medical_ history Check whether the patient has any
other medical history
Check_ patient_ symptoms Check the symptoms of the patient
Need_ of_ Test Does patient require any medical
test
Check _eating _ habits Check the eating habits of the
patient
Check_ medication_ resistance Check the patient’s resistance to
medication
Low_ level_ depression Patient has low level depression
medication advised

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Advice_ anti_ Depressant Advice the use of antidepressant
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The parameters used to make the expert system are the symptoms which are shown by the
patient. So if a patient come, firstly all the questions will be asked by the system and by
answering the first question the system will recognize if the patient has a past history in this
disease, if yes than it will use the information as a parameter to check if the medication taken
in past was effective or not ,and if the patient answers the first question in NO than it will ask
about current medical conditions to check if the patient is suffering from any medical disease
which might have caused this depression, after which it will identify which type of
depression the patient is suffering from, if the initial symptoms fall under the first two
categories i.e. major and Dysthymia it will check the resistance of the patient against the
medicine and if the symptoms fall under the bipolar depression it will raise an alarm for the
doctor and will advice the patient to seek consultation of an expert(psychiatric).a sample
expert system is shown in diagram below:

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The Depression Expert System is illustrated as follows:
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Symptoms Variables Value
Change in weight S1 10
Loss of Pleasure S2 10
Fatigue S3 10
Feeling of Guilt S4 10
Thoughts of Death S5 40
Insomnia S6 10
Persistent Aches S7 20
Mental sluggishness S8 10
Physical sluggishness S9 15
Decreased need of sleep S10 10
More Talkative S11 05
Self Importance S12 05
Thoughts of Racing S13 20
Easily Distracted S14 05
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In this section the algorithm of an expert system is written down in this
algorithm M represents medicine and T represents type of Treatment:
Threshold Rule: if value15 than no depression
Else if value =60 than raise alarm of Dangerous condition
Else If value =50 OR value60 then Dysthymia
Else If value =45 OR value50
Start of Expert System
Rule1: If patient has value=1 then go to Rule2

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Else if value =0 then go to rule 3
Rule2: If treatment (T) working then continue using same medicine (M)
Else if go to Rule 9
Rule 3: If patient has value= (S1 OR S6) AND Value15 then go to Rule4
Else if General treatment (T1) required no signs of depression
Rule4: if patient has value= [{(S1 OR S6) AND (S2 AND S3)} AND (S4 AND S5)]
AND
Value=60 then raise alarm “Dangerous” Major Depression identified
Treatment required
Else if go to Rule 5
Rule5: if patient has value= [(S7 AND S8) AND (S2 AND S9)] AND (value = 50
AND value65) then Dysthymia depression identified
Else if go to rule 6
Rule6: if patient has value= (S10 AND S11) AND value 15 then go to Rule7
Rule7: if patient has value= (S10 AND S11) AND (S12 AND S14) then go to Rule8
Rule8: if patient has value= [{(S10 AND S11) AND (S12 AND S14)} AND S13] AND
(Value =45 AND value50) then Bi-Polar depression identified treatment
required
Else if go to Rule9
Rule9: Depression type cannot be identified please seek expert advice and more tests.

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The design of an expert system for the diagnosis of depression and its different types is very
difficult. To do so, the knowledge engineer would require all the possible parameters for the
system to function correctly. The idea to use expert systems in the field of medicine can
provide a lot of assistance to doctors to help them identify the disease correctly. Lot of work
has been done in this area and there are very complex expert systems being used nowadays.
The designing of an expert system is a very complex part for a knowledge engineer to handle,
control and to solve the problem using multiple variables and constraints. In the near future,
these expert systems will be widely used in almost every field of our daily life making our
lives more comfortable and also providing us with more reliable decisions.

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[1] Hippocrates: http://en.wikipedia.org/wiki/Hippocrates
[2] Melancholia: http://en.wikipedia.org/wiki/Melancholia
[3] Depression: causes and treatment By Aaron T. Beck and Brad A. Alford 2nd edition pp 3-
[4] How common is depression:http://www.overcomedepression.co.uk/HowCommonDepression.html
[5] AI. (2009). Artificial Intelligence. knowledge base expert system. 1 (1), 23.
[6] data base and artificial intelligence http://www.macs.hw.ac.uk/~alison/ai3notes/all.html