Snowden (who really does, apparently, have epilepsy) helps an epileptic.

[MADem]

94. Hyper religiosity and sexuality are pretty major changes, so your very post belies your thesis.

And I've done a little reading on this topic, and sorry--major personality changes ARE possible, and they aren't all focused on depression and anxiety, either. A "hyper-moral" or "ethical" or "religious/spiritual" component is an oft-repeated theme. That's not necessarily a bad thing, of course, but someone who is a party animal can suddenly become serious and overly concerned with ethics, or religion, or morality, or things of that nature.

I've posted a few links in this thread, but here are more (abstracts, a bit of a slog) :

http://europepmc.org/abstract/MED/10496229

A deepening of emotionality with a serious, highly ethical, and spiritual demeanor has been described by clinicians as a positive personality change among patients with chronic mesial temporal lobe epilepsy. Some of these patients tend to be particularly orderly and detailed in their speech and actions (viscosity) and often experience a relative decrease in sexual interest and arousal. These personality changes, distinct from personality changes noted in any other individuals, are subtle in the majority of patients with chronic epilepsy. Patients with the described personality changes may also develop intermittent symptoms of an interictal dysphoric disorder, with episodes of irritable moods that contrast with a predominantly good-natured attitude and for which the patients will be remorseful. The Bear-Fedio Inventory needs to be further modified before it can serve as an adequate instrument for assessing the prevailing personality changes and the intermittent dysphoric symptoms.

http://journals.psychiatryonline.org/article.aspx?articleid=1034926

This study used the Bear-Fedio Personality Inventory (BFI) to compare 41 individuals with temporal lobe epilepsy (TLE) and 37 with psychogenic non-epileptic seizures (NES). Both groups exhibited similar elevations on the BFI, although TLE individuals show greater endorsement of at least one hypergraphia symptom, as compared with those with NES. The correlates of the BFI with demographic and seizure characteristics differed between the groups. These results argue against a specific TLE personality syndrome and suggest that personality characteristics may be related to the experience of having repeated seizures, rather than the specific underlying pathophysiology of temporal lobe epilepsy.

....The concept of a distinct interictal behavioral syndrome in TLE was initially described by Gastaut9 and named by Geschwind and Waxman.10 Characteristic traits included changes in sexual behavior and aggression, increased philosophic and religious concerns, viscosity, and compulsive writing (often referred to as the “Gastaut-Geschwind” syndrome).

In response to lack of evidence for this syndrome with traditional measures of personality and psychopathology (e.g., MMPI, Rorschach), Bear and Fedio developed a scale (Bear-Fedio Inventory [BFI]) measuring 18 proposed TLE behavioral traits and administered the scale to individuals with TLE, healthy control subjects, and individuals with neuromuscular disorders.11 They found that TLE patients endorsed more traits than both healthy-controls and the medical-contrasting group. The traits that were most discriminating included deepened emotions, circumstantiality, altered religious and sexual concerns, and hypergraphia. After Bear and Fedio's publication, a number of studies investigated the BFI instrument and the hypothesis that these personality and behavioral traits were specific to TLE. By and large, studies support the notion that individuals with TLE exhibit increased behavioral traits on the BFI as compared with healthy-controls and other medical groups. There is also recent work showing that individuals with TLE and bilateral hippocampal atrophy endorse more behavioral traits than those with epilepsy and no-atrophy.12 Similarly, Trimble and Freeman found that individuals with epilepsy and increased religiosity endorsed hypergraphia, greater emotionality, and increased philosophical ideas than individuals with TLE with no religiosity.13 There remains significant controversy about whether the syndrome is distinctive to TLE, given mixed findings when comparing individuals with TLE and patients with psychiatric illness or individuals with generalized epilepsy. Several authors suggest that the BFI measures general psychopathology, rather than a specific TLE syndrome.14,15 Shetty and Trimble carefully reviewed findings from past studies and concluded that most studies support the original Bear and Fedio results that the BFI can differentiate between TLE and other healthy, neurologic, or psychiatric groups. They argued that evidence supports a distinct TLE behavioral syndrome.16 They also suggest that the most consistent traits seem to match up with the original Geschwind syndrome (i.e., religiosity, hypergraphia, hypermoralism), suggesting that further refinement of the scale might be useful. Although only a minority of patients develop these syndromes, at least a subset of individuals with TLE exhibit the characteristic interictal personality traits. Whether these traits are truly specific to TLE remains an open question. The current study examines differences between patients with TLE and NES on the BFI. To-date, no studies have been published describing the BFI in individuals with NES. Understanding interictal personality traits in NES may help differentiate patients with TLE and NES in clinical evaluation. It is also of theoretical interest because both patient groups experience seizure behavior, but only the TLE group has pathologic electrical activity in limbic structures. Given previous BFI study results, we hypothesized that patients with TLE would endorse more symptoms on the BFI than those with NES....

http://onlinelibrary.wiley.com/doi/10.1111/j.1528-1167.2012.03602.x/full

Different from frontal lobe epilepsy, which has not yet been evaluated in greater detail, the question of a characteristic organic personality change (“Wesensänderung”) in temporal lobe epilepsy is a continuing matter of discussion (Blumer, 1999; Devinsky & Najjar, 1999; Hoppe et al., 2010). On a phenomenologic level, it is difficult to differentiate the so-called “temporal lobe personality” with deepened emotionality, circumstantial thought, philosophical and religious concerns, hypergraphia, and alterations in sexuality (Waxman & Geschwind, 1975) from anxiety, depression, the so-called interictal dysphoric mood disorder, or memory, word finding and naming problems, which are frequent comorbidities in temporal lobe epilepsy (Gilliam et al., 2004; Kobau et al., 2006). Whereas anxiety and depression refer to Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnoses, the interictal dysphoric mood disorder, in the tradition of Kraepelin, is characterized by an intermittent and pleomorphic symptomatology (e.g., irritability, depressive moods and anxiety, headaches, insomnia, and euphoric states) accompanied also by more positive behavioral features (quiet, modest, devoted, amicable, helpful, industrious, thrifty, honest, and deeply religious). The clinical picture of the interictal dysphoric mood disorder thus ranges somewhere between clinically manifest depression and organic personality change (Blumer et al., 2004). Apart from this, clinically manifest personality disorders can well be observed in symptomatic focal epilepsies (Lopez-Rodriguez et al., 1999; Hermann et al., 2000; Swinkels et al., 2003). The reported rates range from 4–38% (Swinkels et al., 2005). In regard to depression in TLE, it should be noted that the relation between a mesolimbic pathology and depression may be at hand, but that most studies on this issue lack a control group of patients with other focal epilepsies (e.g., FLE). A major reason for the missing clinical control group may simply be that temporal lobe epilepsies make up the majority of the chronic symptomatic focal epilepsies (approximately 80%) in comparison to FLE (approximately 15%), or posterior epilepsies (approximately 5%). Therefore, without a control group of other located epilepsies, specificity of depression and mood problems in temporal lobe epilepsy cannot be taken as guaranteed.

As a concept, “personality” is by definition more trait dependent than state dependent, and particularly in epilepsy it is difficult to determine whether a given behavior has really trait characteristics or not. In epilepsy several factors can be discerned that can lead to dynamic and principally reversible changes in the patients’ behavior and mood states.

Analogous to the multifactorial etiologic model of cognitive dysfunction in epilepsy (Kwan & Brodie, 2001; Elger et al., 2004), changes in personality and mood may be due to epilepsy-related factors such as underlying brain lesions, seizures, and interictal epileptic dysfunction. In addition, psychotropic side effects of antiepileptic drugs (Hessen et al., 2007; Helmstaedter et al., 2008) and reactive factors must be taken into consideration (Tarsitani & Bertolote, 2006). Therefore, for the closer understanding of behavioral abnormalities in epilepsy, the consideration of both, more dynamic and more static factors appears essential. Periictal and interictal epileptic activity can induce cognitive and behavioral problems, and the effects may not be limited to the affected lobe given that propagation of epileptic activity may also disturb neuronal networks beyond the primary lesion or epileptogenic zone (Shulman, 2000). The direct 1:1 influence of interictal activity on behavior in focal symptomatic epilepsy is difficult to demonstrate. Positive behavioral change after successful temporal lobe surgery, however, provides some indirect evidence that seizures and epileptic dysfunction do negatively affect behavior (Lendt et al., 2000; Reuber et al., 2004; Witt et al., 2008).

As for the pathologies, which underlie temporal of frontal lobe epilepsies, these can be more or less systemic and have different onsets within the life span, and thus have different effects on brain maturation and the development of cognitive functions and personality. Lesions can be more stationary like posttraumatic lesions, migration disorders, or developmental tumors or they are dynamic and potentially progressive like in the case of limbic encephalitis, mitochondrial encephalopathies, or tumors. In addition, one must not forget influences of often longstanding antiepileptic medication on patients’ behavior. Antiepileptic drugs may have positive and desirable or negative and adverse psychotropic side effects, and the effects may be reversible, as in most cases, or irreversible (Ketter et al., 1999; Ettinger & Argoff, 2007).

Snowden's epilepsy, we learned from the link at the OP, is adult-onset, and apparently his mother suffers with it as well.