Psychological Concepts

Last updated: March 30, 2026

Sigmund Freud (1856 – 1939)

Sigmund Freud was an Austrian neurologist who pioneered psychoanalysis. His major works include: Studies on Hysteria, Interpretation of Dreams, Three Essays on the Theory of sexuality, Beyond the Pleasure Principle, and Moses and Monotheism.

Freud’s Psychosexual Stages (1856 – 1939)

Freud’s theory of psychosexual development focused on the effects of the sexual pleasure drive on the mind. He believed that at particular points along the developmental path, a body part is sensitive to sexual, erotic stimulations (erogenous zones – mouth, anus and genitals)

Psychosexual stages

Age (years)StageFeaturesNota bene
0 – 1OralGratification is achieved through oral means (breastfeeding)Oral receptive – Fixation in smoking, Oral aggressive
1 – 3AnalGratification is achieved by the child’s perceived ability to control their anal sphincter (defecation)Anal retentive OCPD -, anal
3 – 6PhallicGratification is achieved (in the male child) through awareness of the phallus (penis)He proposed that the Oedipus complex occurs in this stage. The same gender parent is perceived as a hate object due to the child’s love for the opposite gender parent. Sexual suppression starts as the individual is afraid the father might castrate them
6 years to pubertyLatencySexual development is latent as intellectual/social growth becomes more prominentThey can become reserved or develop low self-esteem.
Puberty and beyondGenitalSexual desires are rekindled

Cathartic Model (Freud)

This model was based on the treatment of young females with hysteria (hysteria being an all-embracing term for many neurotic disorders). According to this model, hysterical neurosis was due to repressed, damped-up sexual feelings. These feelings were released (opening up the ‘psychic’ abscess) through hypnosis or free association to resolve the hysteria

Topographic theory of the mind (Freud)

Freud divided the mind into the conscious, preconscious and unconscious.

LevelDescription
ConsciousAware of what is going on outside. Involves current thoughts which are logical, organised, mature and can delay gratification (secondary process thinking)
PreconsciousLies between conscious and unconscious, and contains memories and thoughts that are easy to bring into awareness, but not unless consciously retrieved
UnconsciousConsists of repressed memories that are inaccessible. These are usually primitive and pleasure-seeking with no regard to logic or time (primary process thinking). Commonly seen in children and psychosis. Thoughts and ideas may be repressed because they are embarrassing, shameful, or otherwise too painful.

Structural theory of the mind (Freud)

Freud divided the mind into the id, the ego and the superego. This is his most popular theory. The id is born with, the ego develops at 3 years, and the superego is learnt at 6 years with experiences

ComponentDescription
IdOperates on the pleasure principle. It involves instinctual sexual/aggressive urges and primary process thinking**.** It is unconsciously motivated.
EgoOperates on the reality principle. It is the mediator between the id, superego, and external environment. The ego seeks to develop satisfying interpersonal relationships by using defence mechanisms to control instinctual urges and distinguish fantasy from reality using reality testing.
SuperegoActs as the moral conscience and ego ideal. This is the inner image of oneself that one wants to become. It is derived from internalised representations of significant others in one’s early life, e.g., teachers and parents.

Dream Analysis (Freud)

Freud wrote ‘The Interpretation of Dreams’, in which he stated that dreams represent the fulfilment of repressed wishes. By analysing dreams, invaluable information is provided about unconscious conflicts.

Dream Work (Freud)

Dream work refers to the process by which unconscious feelings (latent content) are converted into the actual recalled dream (the manifest content). Mechanisms of dream work include: symbolization, dramatisation, displacement, condensation, and secondary elaboration.

Transference and Countertransference

Analysis and interpretation of transference and countertransference are important in explorative psychotherapies (psychoanalysis and psychodynamic psychotherapies) where the patient’s early life experiences are explored.

Definition of terms

TermDefinition
TransferenceRefers to the unconscious transferring of feelings that the patient had towards a formative figure, e.g. a parent in the past, onto the therapist in the present setting.
CountertrasnferenceRefers to the feelings unconsciously evoked in the therapist as a reaction to the transference

Defense Mechanisms

Defence mechanisms are unconscious processes that help to avoid experiencing the psychic pain associated with unacceptable conflicts /impulses. These mechanisms are universal and are not necessarily pathological. Freud’s daughter, Anna Freud, produced the first systematic list of the common defence mechanisms. Since then, there have been significant contributions to the list from others.

Defence mechanisms can be characterised as immature, mature and neurotic

Some Selected Defence Mechanisms

Defense mechanismDescriptionExamples
RepressionUnacceptable feelings or memories (e.g. of adverse childhood events) are repressed. This is the most important defence according to Freud. If repression is total, there is no need for other defence mechanisms
RegressionThe person reverts to an earlier, more immature stage of development so that they become more dependent on others. Regression is encouraged in the psychoanalytic settingFixation on the oral stage for smoking addiction or the anal stage for excessive perfectionism/wanting to be in control
DenialThe person refuses to acknowledge reality in order to avoid the psychic pain associated with that realityA patient refusing to acknowledge the fact that he/she is drinking heavily
ProjecitonThe person externalises their own unacceptable feelings and attributes them to othersA person with latent racist feelings projects them onto others, making it easier to justify their own feelings
DisplacementFeelings are transferred from one person/object to another to reduce psychic pain. Freud explained phobias in terms of this mechanism
RationalisationThe person provides a logical (but not wholly true) justification for their or others’ actions to avoid the psychic pain associated with acknowledging the true reasons for the action.“My wife left me for a wealthier man”, when the true reason might have been the husband’s chronic neglect of his wife’s emotional needs
Reaction formationThe person behaves in away that is diametrically opposite to his feelings.Psychoanalysts explain OCD as a reaction to unacceptable feelings of dirt or chaos
SublimationA mature defence mechanism where a person channels and expresses their unacceptable feelings/impulses into socially acceptable actionsExpressing aggressive urges through contact sports such as rugby
Turning against the selfThe patient redirects towards themselves those unacceptable feelings they have against othersMay explain self-harm behaviour
Magical undoingThe patient tries to ‘cancel ot’ an unacceptable thought with an acceptable act.Psychoanalysts explain the compulsive rituals of OCD through this defence mechanism
SplittingThe patient splits objects (persons) into positive and negative aspects (good/bad, caring/uncaring). The person is able to see only one aspect of a person at a time, and not the person as a whole.Self: “ I’m awful”; “I’m wonderful”; Others: “The psychiatrist is uncaring”, “The nurse is caring”
Projective IdentificationThe patient projects their feelings onto an external person, and the latter identifies the role that the patient expects. Interpretation of the countertransference in this situation brings clarity.A patient may project feelings of hate towards the therapist, and the therapist may behave in a way that confirms to the patient that they are indeed being hated by the therapist.

Jungian Analytic Psychology

Carl Gustav Jung (1875-1961), a Swiss psychiatrist, founded the school of analytical psychology after disagreeing with Freud. He introduced the concepts of extraversion and introversion, and divided the unconscious into personal unconscious (unique to each individual) and collective unconscious (universal, common to mankind and consists of symbols and images called archetypes). Jung also wrote about the persona: the outer aspect of one’s personality (’mask’) that others see. He also used the term anumus to denote the masculine aspects of a woman, and anima to denote the feminine aspects of a man.

  • Jungian vs Freudian psychoanalysts
    • Jungian psychoanalysts concentrate relatively more on the patients’ fantasy world and artistic creativity
    • Jungian psychoanalysts are more active in the therapy room (unlike Freudian therapists, who are passive) and reveal personal information about themselves to the patient

Kleinian Object Relations Theory

Melanie Klein (1882 – 1960) laid the foundations of object relations theory by studying infants and very young children through play analysis. She postulated positions: the infant progresses through two stages – paranoid-schizoid and the depressive positions.

Position

PositionDescription
Paranoid-schizoid positionThe infant splits its mother into ‘good’ and ‘bad’ and is unable to see that it is the same mother who provides (’good mother’) and denies (’bad mother’)
Depressive positionThe child comes to see the mother as a whole object consisting of both good and bad aspects. Guilt is prominent as the child fears whether its previous feelings of hatred would destroy the mother. The child realises that the mother can be an object of both love and hate at different times, and learns to cope with this ambivalence.

Reference Intervals
Biochemistry
ACTHP: <80 ng/L
ALTP: 5–35 U/L
AlbuminP: 35–50 g/L
AldosteroneP: 100–500 pmol/L
Alk. phosphataseP: 30–130 U/L
α-AmylaseP: 0–180 IU/dL
α-FetoproteinS: <10 kU/L
Angiotensin IIP: 5–35 pmol/L
ADHP: 0.9–4.6 pmol/L
ASTP: 5–35 U/L
BicarbonateP: 24–30 mmol/L
BilirubinP: 3–17 μmol/L
BNPP: <50 ng/L
CRPP: <10 mg/L
CalcitoninP: <0.1 mcg/L
Calcium (ionized)P: 1.0–1.25 mmol/L
Calcium (total)P: 2.12–2.60 mmol/L
ChlorideP: 95–105 mmol/L
CholesterolP: <5.0 mmol/L
VLDLP: 0.128–0.645 mmol/L
LDLP: <2.0 mmol/L
HDLP: 0.9–1.93 mmol/L
Cortisol AMP: 450–700 nmol/L
Cortisol MidnightP: 80–280 nmol/L
CK ♂P: 25–195 U/L
CK ♀P: 25–170 U/L
CreatinineP: 70–100 μmol/L
FerritinP: 12–200 mcg/L
FolateS: 2.1 mcg/L
FSHP: 2–8 U/L ♂; >25 menopause
GGT ♂P: 11–51 U/L
GGT ♀P: 7–33 U/L
Glucose (fasting)P: 3.5–5.5 mmol/L
Growth hormoneP: <20 mu/L
HbA1C (DCCT)B: 4–6%
HbA1C (IFCC)B: 20–42 mmol/mol
Iron ♂S: 14–31 μmol/L
Iron ♀S: 11–30 μmol/L
Lactate (venous)P: 0.6–2.4 mmol/L
Lactate (arterial)P: 0.6–1.8 mmol/L
LDHP: 70–250 U/L
LHP: 3–16 U/L
MagnesiumP: 0.75–1.05 mmol/L
OsmolalityP: 278–305 mosmol/kg
PTHP: 0.8–8.5 pmol/L
PotassiumP: 3.5–5.3 mmol/L
Prolactin ♂P: <450 U/L
Prolactin ♀P: <600 U/L
PSAP: 0–4 mcg/mL
Protein (total)P: 60–80 g/L
Red cell folateB: 0.36–1.44 μmol/L
Renin (erect)P: 2.8–4.5 pmol/mL/h
Renin (recumbent)P: 1.1–2.7 pmol/mL/h
SodiumP: 135–145 mmol/L
TBGP: 7–17 mg/L
TSHP: 0.5–4.2 mU/L
T4P: 70–140 nmol/L
Free T4P: 9–22 pmol/L
TIBCS: 54–75 μmol/L
TriglyceridesP: 0.50–2.3 mmol/L
T3P: 1.2–3.0 nmol/L
Troponin TP: <0.1 mcg/L
Urate ♂P: 210–480 μmol/L
Urate ♀P: 150–390 μmol/L
UreaP: 2.5–6.7 mmol/L
Vitamin B12S: 0.13–0.68 nmol/L
Vitamin DS: 50 nmol/L
Arterial Blood Gases
pH7.35–7.45
PaCO₂4.7–6.0 kPa
PaO₂>10.6 kPa
Base excess±2 mmol/L
Urine
Cortisol (free)<280 nmol/24h
Hydroxyindole acetic acid16–73 μmol/24h
Hydroxymethylmandelic acid16–48 μmol/24h
Metanephrines0.03–0.69 μmol/mmol cr.
Osmolality350–1000 mosmol/kg
17-Oxogenic steroids ♂28–30 μmol/24h
17-Oxogenic steroids ♀21–66 μmol/24h
17-Oxosteroids ♂17–76 μmol/24h
17-Oxosteroids ♀14–59 μmol/24h
Phosphate (inorganic)15–50 mmol/24h
Potassium14–120 mmol/24h
Protein<150 mg/24h
Protein/creatinine ratio<3 mg/mmol
Sodium100–250 mmol/24h
Haematology
WCC4.0–11.0 ×10⁹/L
RBC ♂4.5–6.5 ×10¹²/L
RBC ♀3.9–5.6 ×10¹²/L
Hb ♂130–180 g/L
Hb ♀115–160 g/L
PCV ♂0.4–0.54 L/L
PCV ♀0.37–0.47 L/L
MCV76–96 fL
MCH27–32 pg
MCHC300–360 g/L
RDW11.6–14.6%
Neutrophils2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes1.0–4.5 ×10⁹/L (20–45%)
Eosinophils0.04–0.44 ×10⁹/L (1–6%)
Basophils0–0.10 ×10⁹/L (0–1%)
Monocytes0.2–0.8 ×10⁹/L (2–10%)
Platelets150–400 ×10⁹/L
Reticulocytes0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time10–14 s
APTT35–45 s
Paediatric
Pulse Rate (bpm)
Neonate140–160
Infant <1yr120–140
1–5 years110–130
5–12 years80–120
>12 years70–100
Respiratory Rate (tachypnoea)
0–2 months≥60/min
2–12 months≥50/min
1–5 years≥40/min
>5 years≥30/min
Blood Pressure (mmHg)
Term65/45
1 year75/50
4 years85/60
8 years95/65
10 years100/70
Weight Formulas
3–12 months(a + 9)/2 kg
1–6 years2a + 8 kg
>6 years(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn13–20
1 month11–18
2 months10–15
1–2 years10–13
>2 years11–14
MUAC (6 months–5 years)
Obese>17.5 cm
Normal13.5–17.4 cm
At risk12.5–13.4 cm
Moderate malnutrition11.5–12.4 cm
Severe malnutrition<11.5 cm
Developmental Milestones
Social smile1.5 months
Head control4 months
Sits unsupported7 months
Crawls10 months
Stands unsupported10–12 months
Walks12–13 months
Talks18 months
CSF WBC (/mm³)
Term newborn0–25
>2 weeks0–5
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